Schools can't teach everything. They need to teach people to read, write, think critically, how to find information.
They do not need to teach about any particular sexual practice. Just what measure are needed to be safe.
They need to teach consent and boundaries. People should only ever be involved in sex that they enthusiastically consent to.
I would tell them to be wary of men who like to talk about lesbian's sex lives, as by definition it is nothing to do with them.
And be very wary of men who can't see how inappropriate that is, even after he's been specifically told so.