form my personal opinion.........
it's no point that your child study one day before exam since there are many days for preparing exam, one day for rest(few hrs......with no harm). With target,he can concentrate in the earlier holidays,not thinking his fds and the rsults of the event, while others are playing around.With targets ,he would not regret that he has missed the important game!
It's a matter whether you trust/support him or not. It's golden time to build up mutual trust relationship.
Also,The 1st exam of F1 is not that important( not final/HKCEE). I trust your son even though I don't know him very much but I know he is a boy who can keep "promise is promise". As some told me that he keeps studying everyday and of course he can concentrate on different activities and hobbies.His result is around middle of class(the happiest group,I think haha)
So no worry for his displine la, if exam reults are not as good as expected, then he have to bare his responsibilty!
It's all about planning,put the deadline earlier.