Grade 10 summer should be spent casually going about. If at most, you want to busy yourself, volunteer at something you care about, go exercise, take up a hobby (learn a new instrument perhaps?), but relax. Unless you rely too much on being spoon-fed knowledge (as many high schoolers are), you shouldn't stress about grade 11, it's relatively easy. Just pay attention, take notes as needed, ask questions immediately if you're confused, and research anything you want to learn more about.