Hmm tough question!
Erm! Not entirely sure here! At my school (years ago now) we were given a Sex Education class on Periods, Tampax and Sanitary Towels ect. They were actually quite useful and I remember thinking about what the class had said the first time I used Tampax.
On the actual sex side of things I think that most of it was ignored or found to be highly amusing. I think I was only 12 when we started those classes so as a class we just enjoyed laughing and watching funny cartoon sex education video's ect. I don't distinctly remember anything being of any dramatic usefulness and the only thing I remember from this class was watching the cartoon videos and also a video of a woman giving birth.
I think my parents gave me the most useful information. But sex education classes should be about clearing up misunderstanding that young girls and boys have about sex ect.
Like that it is possible to get pregnant on your first time,
It is possible to get pregnant if you've not started your period.
Also a good understanding of contraception should be given. Where to get them and the importance of patient doctor confidentiality in regards to teenage pregnancies and contraception.
These are the important things. Getting the facts out there so that young girls and boys have accurate information and so can make informed decisions.
Again I got most of my information from my parents.
I'd say the classes are useful as long as they provide you with accurate information that you didn't previously know!
Good Luck!