Most teens can't wait for Christmas vacation to take a break from school. However, students who are struggling should spend some time each day reviewing material that was difficult . (There are numerous sites with online practice in nearly every subject. Just google something like: "free practice worksheets with answers for solving inequalities" or check out the sites listed below.)
Seniors need to work on college applications and juniors need to be researching information about colleges they are interested in attending. In 3 Tips to Keep Your Teens Focused, the author provides some useful ideas on how to help your teenager complete tasks during break.
Vacation shouldn't just be about school related work. Top Ten things to do with teenagers during Christmas offers some creative ideas to stay engaged with your teen and to have some fun!
Here are some websites that offer free online practice in most subject areas:
http://student-tutor.com/blog/top-10-math-websites/
http://larryferlazzo.edublogs.org/2008/12/07/the-best-sites-for-grammar-practice/
http://www.shmoop.com/learning-guides/ (all subjects)
https://www.khanacademy.org/ (all subjects)