To start off, I think it depends on the subject. For subjects like Methods, Chemistry etc you should try and finish the course before school starts again - do the exercises and make notes. This is so that once you get back to school, you're ahead and it saves you time. Your teachers will go over the course material and this reinforces what you've learnt before (in the holidays) - consolidates your knowledge.
For "ROTE-learned" subjects like Legal Studies, I've just been writing summary notes of each AOS. For English, I'd just read all your texts for next year. I think to answer your question, it's both - to revise what you've learnt over the break and to get a deeper understanding - ask your teacher if you're unsure of anything.