Encourage students write to their representatives about an important issue or to congratulate them on winning an election. It will encourage them to think critically about important political issues and give them a chance to do something about it! You can easily find sample letters online to help students get started.
Attached is a sample letter and instructions (which you'll need to modify to fit your own congressional district). Once students submit their letters, have them mail it to their representatives and see what happens. Sometimes they write back, more often they don't, and that's okay. What's important is students to get a sense of civic participation and influence on policy.