I usually spend the first couple of weeks of a new school year revising vocabulary and structures from the previous year, or if the students are new to the academy, on diagnosis of what they already know. This is partly because normally the new coursebooks haven't yet arrived (or in some cases been ordered!) but the real reason is that the vast majority of learners have hardly touched English for the whole summer. They have abandoned all contact with the language for two to three months! This is a more serious problem for very young learners, for whom three months is a lifetime. They therefore need plenty of revision and practice of what they have previously learnt, before they go on to a new course. Of course, many coursebooks start of gently, including some revision, but I usually find that this is not quite enough.
One of the problems with revision, is that younger learners recognise that they have studied the concepts before and therefore feel that they do not need to look at them again, complaining that it is too easy and they have "already done it". What I usually try to do to prevent this is to make the revision into game-like activities. For example, I am currently revising "can/can't" for ability with a group of 9 year-olds, before we move on to the same structure for asking for permission and requests. After practising a little at the end of last lesson, today I will be presenting them with a list of "challenges" to try out, where they will complete a worksheet in pairs or small groups and present their feedback to the class. The challenges are things like: Can you write 10 animals in English? or Can you say the English alphabet? or Can you name all the rooms in a house? This also revises vocabulary so it is a good idea to change the questions according to what the class have previously studied. They have great fun trying to complete the challenges, and then afterwards I ask them some questions about what they have discovered.