From my own school career I would say I was frequently and often told things that are known not to be true by those teaching them to me (I know this because those same teachers taught me truer versions later).
Here's some examples:
Light is a wave.
There is no square root of a negative number.
The square root of 16 is 4.
Pretty much any chemical equation you care to mention.
Newtonian physics.
Teaching involves simplifying, often to the point of untruth, and that's not a bad thing - it's almost certainly necessary in order to impart a appropriate level of knowledge to classes in a progressive manner.
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