My school didn't allow study leave, but did allow exam leave when I sat my GCSE's last year. I think they do it so that the less hard-working people at least get some revision done in supervised conditions in order to get the best possible grades. Also the teachers are there to help with anything you find tough, and are not a journey away. It is unfair that everyone has to suffer for the minority who wouldn't work but I think it is better. For the new a-levels, we don't even get exam leave so count yourself lucky!