These kids were in high school; sophomores and juniors so we're talking probably 16 and 17 years old.
Think back to when you were that age and how much "control" your parents had over you. Not much, I'd bet!
All it would take is an hour (if that) and the video would be done. I don't think there's any possible way that the kids' parents can be blamed for this, other than not imprinting into their kids' heads that they should abstain from sex for as long as possible.
What I don't understand is why they were expelled. Did they break school rules? Is there a rule somewhere that says "you cannot attend if you are sexually active"? Or was it more of an "elite" thing because it was a private school and they didn't want their reputation sullied?
I definitely think a challenge to the school board is in order, although the parents will probably be too embarrassed and mortified to put up a fight.
I hope they at least used condoms.