My DH is a public school teacher, and here the survey is given as well. I think it's called the Healthy Youth survey (or something like that). All sorts of questions are included about s*x, drugs, alcohol, and also healthy relationships (do you feel you have a parent/adult you can talk to about...etc). The survey is totally anonymous, there are opt out forms sent home and the results are used to inform instruction (kids in general need more guidance in...this new suchandsuch a curriculum seems to be helping, etc), and it is tied to grant money in some way (it's a national thing as far as I know; not everywhere does it, but it is super common).
The biggest problems I (and my husband) see with it are...as young as it is given here (6th grade), there is a level of suggestibility (if you're asking about it, it must be common, maybe I should try it type thinking) and the results are for the current students, and by the time the results are back, those kids have moved on to the JR high and they have new kids (does still help with overall trends though), also, a lot of kids aren't very truthful most likely.
Anyhow, I don't think it is a horrible evil thing, I don't know how totally needed it is, but I do know that lots of schools give it.