kalo primary school ni smua like zhann said...lots of revision books avail, even online. But sec school kids nih, their main prob is they think that they dont't have enuf time. So, perhaps, you can start by making a timetable on what subj to revise. Per subj, 30-35min enuf. If she is weaker in a particular subjects, just repeat the revision again at the later part of the day. Encourage her to do lots of mind-mapping (look for Tony Buzan resources) and various studying techniques that helps her to remember facts.