We have 3 groups of children (wish so much it was only two and life would have been SO much easier if it had been) like you we are using just the one set of toilets and oh my goodness, how may times a day we are cleaning them!! Really- i's ridiculous- none of the children ever seem to want to go together, or even two from the same group. It's always one from one group- toilets get cleaned then someone from another group, toilets get cleaned, then someone from the first group and so on- drives us batty.
That's of no help to you at all, is it! Sorry more agreeing with you really. I'm also thinking this cleaning is going to have to continue in Sept- more so if we're not working in bubbles, isn't it?