Note, by primary school I mean as opposed to secondary (ie pre-high school) not just kindergarten. These sorts of misconceptions are a big pet peeve of mine, and I'd like to make a list of them, so I'm hoping you guys can help me out. I'll start us off with three of them:

Red, Yellow and Blue are the primary colours.
In fact, Red, Green and Blue are the primary colours (specifically, the primary colours of light. Red Yellow and Blue aren't even the primary colours of pigment, however: Those are Cyan, Magenta and Yellow). RYB can't reproduce every colour in the visible spectrum like RGB and CMY can, and not only that, but RYB has a significant bias toward browner colours. It may have been used as the 'primary colours' of pigments more than a hundred years ago, but I would think teachers would be able to get with the times and stop teaching this fallacy.

Everyone thought the world was flat until Christopher Columbus proved them wrong.
I really hate this one. It has been known since the time of the ancient egyptians and greeks that the world is round, and I believe the egyptians even measured the diameter of the earth, by measuring the length of the shadows cast by two different pyramids at different latitudes during the winter solstice. This one also ties in with the idea that Columbus was the first to 'discover' America, which completely disregards the vikings that came 500 years earlier, and the native population which has been there for something like 10000 years.

The earth's seasons are caused by the change in distance between the earth and the sun and the solstices/equinoxes mark the beginning of each season
This one is covered quite adequately on one of the BA pages, so I won't go into detail about why these are oh so very wrong.

Anyone have any more?

"The earth beneath the crust is an ocean of bubbling hot lava - sometimes the crust breaches, and lava spills out - this is what we call a volcano"

Quite popular, even to higher grades. In fact, the earths mantle is almost completely solid. There is the athenosphere (depth ~200 to 400 km), where you can have up to a few percent molten rock (called magma), but beside that, the mantle is solid (if fact it behaves plastic over long timescales). Temperatures in the mantle would be high enough to melt rock under surface conditions, but the pressure of the overlying rock is so high it won't allow the rock to melt.
Volcanos exist because either you have decompression (through stretching of the crust, e.g. at midocean ridges) or because you add some water to the rock (via subduction), which allows the rock to melt even at high pressures.

Actually, my teachers taught this one mostly right. RGB being the primary colours of light, (I can't remember what they taught as the primary colors of pigment, but it wasn't CMY) and that light is additive while pigmentation is substractive.

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In Fallout 3, 'happiness' is a warm junkyard dog and a loaded gun. It's mostly the loaded gun.
- Moose's one-line review.

"your going to regret that one. You are now a colonoscope...
- Chrissy, corrupting PraedSt's wish.

Aside from some political misconceptions that I won't go into here, my second grade teacher tried to tell us that atmosphere held in the gravity.

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Forming opinions as we speak

I'll follow your lead and stay away from history and politics; and just say my memory of the information portrayed was that it was innocent and ignorant revisionism at best, propoganda at worst.

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Don of Borg - Cool, Calm, Collective.

"Within the next generation I believe that the world's leaders will discover that infant conditioning and narco-hypnosis are more efficient, as instruments of government, than clubs and prisons, and that the lust for power can be just as completely satisfied by suggesting people into loving their servitude as by flogging them and kicking them into obedience." -- Aldous Huxley

I agree to some extend with uniqueuponhim, but the example Bynaus came up with is an example of what in The Science of Discworld was called "Lies to Children", ie. a simplified explanation that may be wrong in all details but nevertheless is a helpful steppingstone towards the next level of understanding.

Without the partial understanding given by previous levels of simplified versions, there will not be enough hooks to hang the next on.
Pressure/temperature phase diagrams of rocks won't help schoolchildren in grasping that the earth is very hot on the inside.

If you give it a though, your explanation is a simplification just as the example you gave, just a simplification aimed at a more knowledgeable audience.

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And the "driving on the freeway on a scooter" analogy still holds true because the pilots are sitting in 7 to 30 ton aircraft o' doom and you are running around them in your very own Meatbody, Mark I. Beep, beep.
Trying to make sense of computers, The Error Log.

This measurement was performed by Eratosthenes around 250 BCE. It was noted that at the time of the June Solstice (summer solstice for the Northern Hemisphere) that the Sun shone straight down into a well at Syene in upper Egypt. On that day the shadow at Alexandria was 7.5 degrees to the vertical. The distance from Syene to Alexandria was about 500 miles, 7.5 degrees is about 1/50th of 360 degrees, so the circumference of the Earth was estimated at 25,000 miles, not too far from the correct value of about 24,900 miles. I don't think any pyramids were used in the measurement; sticks sufficed and were easier to measure.

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Microsoft is over if you want it.

The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

A slight addition to this is that the distance between Syene and Alexandria he used was approximated from the speed of a camel and the time it took to travel between the cities, and the measure he gave was in a unit noone knows for sure how long is, but the best estimate we have results in nearly the right size of the earth.
Whether that estimate was partially based on his measure of the size of the earth is anyone's guess.

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And the "driving on the freeway on a scooter" analogy still holds true because the pilots are sitting in 7 to 30 ton aircraft o' doom and you are running around them in your very own Meatbody, Mark I. Beep, beep.
Trying to make sense of computers, The Error Log.

Weird. I've been working on this problem for the last several
days. I was using web references to help me select and name
colors for a color wheel just thirty seconds before reading the
first post in this thread.

I disagree that there is anything wrong with calling yellow a
primary color. It is a primary color.

I also disagree that there is anything wrong with calling red
and blue primary colors of pigments. They are primary colors
of pigments.

There are basically three situations:

Additive colors -- primary colors are red, green, and blue.
As in TVs and computer monitors. Different colors of light in
close proximity on the retina add together to make new colors.

Subtractive colors -- primary colors are red, yellow, and blue.
As in tempera and oil paints. Light incident on a surface is
selectively reflected or absorbed by pigments. Reflected colors
are able to reach the eye.

Transparent colors -- primary colors are yellow, cyan, and
magenta. As in printing ink and watercolor paint pigments.
Light incident on a surface is selectively transmitted or
absorbed by pigments. Transmitted colors are reflected by the
underlying white base material and able to reach the eye.

I just told my mother yesterday how I discovered in first grade
that yellow crayon and violet crayon overlapping made brown.

Naturally, when using subtractive colors, more pigments mean
fewer colors of light reaching the eye. That is what happens
with pigments. Naturally, combinations of pigments will tend
toward brown. Combinations of light tend toward white.

Yellow, red, and blue are taught as the primary colors because
those are the primary colors of the media available for young
children to use in schools. Most typically, tempera paint.

I think of the primary colors of printing inks in the order
YCM rather than CMY since that is the order in which they are
laid down-- from lightest to darkest.

-- Jeff, in Minneapolis

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http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

All very reminiscent of the aliens in Cohen and Stewart's book "Evolving the Alien", where the alien teacher character has a title which translates to "Liar to Children".

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"The truth may be out there, but lies are inside your head" Terry Pratchett

Every science and astronomy text that I've ever read or consulted states that the seasons start with the equinoxes and solstices. Until finding this board back in 2001 I had never read nor heard anything different.

Cases in point:

Link 1

Link 2

Link 3

I'm pretty sure the whole "beginning of a season" debate started when meteorological considerations were brought into the picture, i.e., how can it still be summer when the weather is so fall-like? Of course the problem with using the solstices and equinoxes as the midpoints of the seasons is that in the northern and southern temperate zones, this shift of weather conditions becomes even more extreme.

For example, having spring start around February 5th in northern New England won't cause the deep snow, blizzards, and crowded ski areas to go away.

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I'm a bit rusty on this, and was not aware of the 3rd item, the Teansparent colors.

Must be having a brain fart, but I can't remember how you get yellow out of the additive method.

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Don of Borg - Cool, Calm, Collective.

"Within the next generation I believe that the world's leaders will discover that infant conditioning and narco-hypnosis are more efficient, as instruments of government, than clubs and prisons, and that the lust for power can be just as completely satisfied by suggesting people into loving their servitude as by flogging them and kicking them into obedience." -- Aldous Huxley

I was in elementary school from the late 1950's to mid-1960's,
so it's been awhile. I don't remember anyone ever saying that
everyone thought the world was flat, except in situations where
such statements were intended as humor or sarcasm.

Do you know of an actual case where a teacher told students
that everyone thought the world was flat at the time Columbus
was proposing his trip to the west? I doubt it.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

You're alluding to the diurnal heat lag, if I'm remembering the term correctly from climatology and meterology classes. The warmest day of the year typically follows the day with the most sunshine by about a month and a half, and the coldest day of the year follows the day with the least sunshine by the same lag. (At least here at 45 north latitude).

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Don of Borg - Cool, Calm, Collective.

"Within the next generation I believe that the world's leaders will discover that infant conditioning and narco-hypnosis are more efficient, as instruments of government, than clubs and prisons, and that the lust for power can be just as completely satisfied by suggesting people into loving their servitude as by flogging them and kicking them into obedience." -- Aldous Huxley

Blue and green.

__________________
In Fallout 3, 'happiness' is a warm junkyard dog and a loaded gun. It's mostly the loaded gun.
- Moose's one-line review.

"your going to regret that one. You are now a colonoscope...
- Chrissy, corrupting PraedSt's wish.

Don't know quite where they got it from, but university freshmen are quite commonly of the opinion that lunar phases are caused by the Earth's shadow. I may recall an opinion column (S&T or somewhere) suggesting that this came from an inappropriate introduction of eclipses before phases.

Another one - that gravity is connected to spin, maybe a result of experimenting with ropes and buckets of water. This can enter in getting the causality between mass and gravity backwards (I've had answers suggesting that Jupiter became so massive because its rapid rotation gave it powerful gravity). Come to think of it, it seems to be really easy in the abstract to confuse the workings of magnetism and gravity.

I was recently on the dissertation committee for a Ph.D. in education, whose project dealt with the role of religious beliefs in elementary science instruction. She found stuff that would make most of the ACLU cringe, but what really made her have to sit on her hands during classroom observation was the generally poor level of science preparation of the teachers, despite being selected as the ones who felt introducing science was important, and the really really poor level of support from the schools and systems. Indeed, sometimes they were flying by the seat of the pants when in unfamiliar territory. In thise case, what's interesting is that the same folk answers seem to recur all over the map.

Red light plus green light add together to appear yellow.
That is why yellow is such a bright color: It involves a lot
of light-- most of the spectrum-- including green, to which the
eye is most sensitive. Of course, it is also possible to have
a narrow bandwidth of just yellow light, with no red or green.
It would have to be fairly intense to stimulate both the red
and green receptors in the eye sufficiently to appear as bright
as a wider spectrum.

-- Jeff, in Minneapolis

__________________
http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves

My teacher tried to tell us that lightning is actually cold-fusion and that the temperature inside a lightning bolt is near absolute zero...