Although I believe moomcups can be great for some people in some circumstances, I don’t think they should be the go to option here.
These are girls who may be horribly embarrassed about their periods, due to struggling each month. Giving them a device they have to empty in the cubicle then carry out to the sinks potentially with bloody hands, then back into the cubicle to reinsert... well, I can’t inagine many school girls managing this in the school environment with so little privacy.
Also, remember that a proportion of these girls aren’t able to access sanpro because of their parents eg a father refusing to believe it, or a mother deciding she won’t be there for her daughter (and yes, it’s not just fathers / Male carers, women do this too).
In this situation, the girls need discrete sanpro which is disposable, as they will not have any ability to wash fabric pads or dry them openly. Moon cups may answer that, but should only ever be one option of many, as trying to get to grips with inserting and taking out a device would be a step too far for most girls I suspect.