I believe that students need to take a couple of weeks right after school is out and have fun! They have been cooped up, studying hard and walking that line of following rules and being told what and what not to do for quite a while. They have been stressed with finals and trying to get every last good grade possible to ensure either passing to the next grade or upping their GPA's . Summer continues to get shorter and shorter with schools starting now at the end of July, so let them be kids, have fun and relax. Now this is not to say that maybe reading a book here and there or prepping for SAT's or other important tests should be totally forgotten but on a bit of a slower pace than in the regular school year. Getting on the internet and using educational resources and tools that make learning fun and not feel like school is a good way to keep their minds sharp also. Traveling is one of the most educational experiences there is if possible over the summer...maybe take them somewhere new with a lot of history and legendary stories. I do not think kids should sleep their summer away, but I also believe they deserve some leniency...after all they will be all grown up sooner than you can blink and have to join adult life!
It could be the perfect time to get them a tutor though while they are away from the pressures of school to help them prep for upcoming tests and classes that have deemed difficult.