This site offers some sound advice for both students and for parents on may topics, including how to study effectively and reduce distractions: I encourage both students and parents to have a careful and thorough look around this site – it has some really good advice for when you are having a difficult time as well – search through the ‘what’s on your mind’ tab under the ‘For Young People’ or ‘For Parents’ tab.
This NZ site is very useful for study guidance for Maths, Science and English: