State testing may be finished, but is the curriculum?
This can be a great time of year for the kids to take on "independent research." Not sure what grades you teach, but by this point in the year, the kids are tired of sitting still, and all the testing, and so on. This is the time of year when hands-on activities are imperative. If you have outside activities, even better!
Think about having groups of students design their own experiments, and carry them out the last few weeks. I have done summer programs where we covered solar energy, and had students design their own solar (pizza box) ovens, then we did some testing, modification, and finally, a competition to see which worked the best. The s'mores were pretty tasty too!
Learn, but also have some fun, those last few weeks. That will do more toward keeping your students motivated, engaged, and curious over the summer, and hopefully, they will come back excited and ready to learn in the fall.