I think talking about it being normal/healthy and a safe way to experiment is worthwhile. As a teacher (and I'm a biology teacher, so I do teach sex-ed type stuff sometimes) I think I'd be really uncomfortable with anything more than that. The problem is, it's hard to say something like that to a class and just move on. They will have questions and different beliefs and I think I'd find that quite a tricky discussion to manage.
I think boys are given lots of messages e.g. by the media that it's normal to masturbate, whereas girls aren't, and I do think that's something I'd need to combat.
I understand it's not really about my comfort, but equally teachers often lack training in teaching sex-ed or any PSHE topics, really. I think sometimes teachers with limited training/information can do more harm than good, and often the way sex-ed is taught in schools is really disjointed. Biology teaches some stuff, other stuff is taught in PSHE, parts of it are covered by the RE curriculum and so on!
It would be great if all teachers got proper training about teaching sex-ed and it was delivered in a formal, joined up way.
I do think a lot of stuff is taught too late in schools. I teach about contraception in Y10 (this is partly due to where it falls on the GCSE curriculum), but students in my school only get the chance to have a talk from a Brooke sexual health nurse in Y11, when they are 15/16. Personally, I think that's too late, and they need more input around 13/14.