Since many homeschoolers are planning next year's curriculum purchases, I thought I'd give a few of recommendations we'd have used ourselves, yet for various reasons we weren't able to.
HSLDA has a highly rated government course for high schoolers called Constitutional Literacy with Michael Farris.
Furthermore, HSLDA also provides Generation Joshua clubs around the country, provides hands-on experience in civic training for young people. They also have scholarship opportunities, as well as coursework to count towards government. There is even a book club! Additionally, they host igovern, which is a week long summer camp!
If I had it all to do over again, I'd revamp our school studies to fit these opportunities in for my kids. My son now attends Patrick Henry College and I see the fruit of these programs. I highly recommend them!