I've only recently realised how privileged I was to have as much sex education as I did at school, and even that had considerable gaps seeing as it was, to my memory, focussed entirely on straight people. I mean I really didn't appreciate it at the time, I was 13, but the point is that there are kids that young who have sex, and they need to be safe. Perhaps it's hypocritical of me because this is a really strongly held belief of mine, but I really do think that regardless of whether the school is a faith school or not, sex ed should be provided. Sex ed isn't about endorsing sex at young ages, but giving people the tools to understand it, and how to protect themselves and others (also there is so much evidence that suggests that teaching abstinence is completely counterproductive). Thankfully nowadays we have the internet and there are some great resources available for sex ed, but there's no guarantee teens will be able to access that. And I say this as someone who's asexual and will very probably never use most of what I was taught in sex ed. But even for me there was a lot of important stuff about periods and whatnot that I needed to know, and things that I didn't understand even with a fairly decent education. Ignorance is so dangerous and maybe it's the fact I work in healthcare so I'm aware of the importance of knowing how your damn body works and how to keep yourself safe where possible but I do not think anyone's religious beliefs make it ok to send kids out into the world with no understanding of sex. It's irresponsible and it's immoral, if your religion prohibits sex before marriage that is absolutely bloody fine but once people get married? If they want to have sex they're going to need to understand fundamental stuff about how that goes down. I think part of my issue is that sex ed is usually tied into reproductive education and when we deny people sex education we're often denying them other information about how their body works (see my above point about periods, it is completely wrong not to teach people anything about what's going to happen to them once a month).
Long story short, yes. Keep kids safe. I think those classes also need to incorporate important lessons about consent, and your ability to say no at any time, and that being drunk removes your ability to consent, and also giving kids who aren't straight the tools to be safe too. Funny how we still ignore that in sex ed despite the fact that the lack of decent sexual education for LGBT+ people was a major contributing factor to the AIDs epidemic and led to a lot of deaths. But what do I know.