Don’t procrastinate
It may seem tempting to just forget everything that you have learned throughout the year in order to give your brain a break, but it is best to keep yourself in line and get tasks over with so that you are not forced to stress later on.
Ask teachers for extra materials from their class
Get in touch with teachers that are currently teaching the IB and AP classes that you will take next year and find out what is going to be taught, and how you should prepare, etc. This will help you balance out your time during the summer, when thinking about a work schedule.
Study the materials
Go the library and check out books pertaining to the classes that you will take next year. There are many good books available according to different subjects. Barron’s has good books for a variety of subjects ranging from Algebra I to Physics. Both Barron’s and The Princeton Review offer books on AP exams, which can be used healthily throughout the year, as preparation for the exam in the end of the year. Cambridge is a number one resource to find books for courses in the IB Diploma realm, and is largely used for the backbone of most IB course curriculum.
Jump-start your class (Kaplan, C2, etc)
There are many out-of-school programs with summer workshops for AP and IB material, which can help you jump-start your path to success in courses requiring a different level of thinking. If you are down to the last two to three weeks of summer, and have not prepared at all for your classes, this may be a good choice for you. While these programs can be more on the expensive side, they can be beneficial if you are a slower learner and want to get a head start your classes.