Y10 is the time to learn how you revise best and what resources you find useful and what don't work for you.
It's the time to badger DM into buying you revision guides and your own copy of the text book when there is no guide (excel Geog we are looking at you).
It's time to learn your way round the schools computer system, if you haven't already (DDs teachers have been very slow getting to grips with it themselves, so you have to keep looking).
It's a time for drawing mind maps and writing record cards. It's a time for badgering the teacher about topics you just don't get.
Y10, now there aren't stupid modules, should be about learning how to revise in a way that suits you and finding that you have learnt the work along the way.
Y10 revision isn't measured in hours spent staring at books, but in skills learnt.
Of course DC should have learnt all this in Y8 and Y9, but they don't, certainly not completely. Because subjects they loath and are going to give up get in the way and because they haven't yet knuckled down to the compulsory ones they dislike.
Y10 is for real, use that fact carefully, do not set tar keys DCs will instantly see as impossible.
As for HT, my DDs trampoline, cycle, swim, go out for the day. See DFs, DD1 often spends three days of her 1/2 terms on music courses.
Teens don't just face book and play on their Xboxes, they have a life.
And smug teacher up thread, no DD1 won't get As she's dyslexic. If she revised 12 hours a day she wouldn't get A in written exams. (She would with 2hrs a day and a scribe, but she doesn't qualify for more than extra time).
There is more to life than A* as I know all to well.