I know at least two facts from school physics appeared to be wrong.
Odor spreads around a room due to diffusion (actually due to air flows. Spreading by diffusion in still air would take a couple of years-it's too slow).
Coriolis force makes water vortice in a sink (it may. In a very still water and under other ideal conditions it may give a very slight effect. Not in every-day life).
There are quite a few fallacies that have made it into school textbooks. The most common ones have been collected here: http://www.eskimo.com/~billb/miscon/m...
One misnomer that I found to be potentially confusing is that something 'lighter' than a fluid floats on it; while actually 'lighter' over here means 'of less density', it is at most times confused by a kid, reading it for the first time, to be 'of less weight'.
Odor spreads around a room due to diffusion (actually due to air flows. Spreading by diffusion in still air would take a couple of years-it's too slow).
Coriolis force makes water vortice in a sink (it may. In a very still water and under other ideal conditions it may give a very slight effect. Not in every-day life).
Can you think of smth else?
PS. Sorry for my loosy English.