Learn new content or revise and consolidate old?

Hi, seeing as it's now holidays, I had hoped to push ahead in Bio, chem and maths and go into every next lesson already knowing the content. However, I realized i could be doing exam questions on everything we've covered in school and mastering it.

So this is to anyone with experience, what do you think works better!!?? Should I push ahead and keep ahead of lessons (although I may still need to revise and practice older topics first). I'm aware that I could do both, but I could get further into the content if i wanted and temporarily leave the old content for a later time.
Im a little confused on what to do lol, thanks