While I think it's important that kids should be able to talk to parents about sex, the sad truth is that parents are going to have different amounts of knowledge and differing opinions on the subject - some opinions are likely to be very negative and damaging, and a lack of knowledge on the part of a parent can lead to much bigger problems down the line.
Sex education programs in school tend to be pretty straightforward and, if not sex-positive, at least neutral. Of course, abstinence-only teachings that some schools use can be just as damaging, since teens who want to have sex are going to regardless (truthfully, I don't think sexuality has "grown more and more" among young people - it's just more openly acknowledged now). It's best if they're taught about contraception, as well, and some sex education classes actually skip over that subject or put it in a negative light.
I'd hope that both options would be available to growing young people, but I can't say which option is better because it all depends on what, precisely, is being taught, and how the teacher or parent goes about it.