Allow ALL taxed U.S. citizens and workers the right to vote, subject to a test on basic government knowledge.

The easiest way to say this is Patrick Henry's famous phrase: No Taxation without Representation.
I'm a young teen in high school and, while unemployed now, have been working for 2 years and have been subject to government taxes, just like the millions of other citizens in the labor force. I believe that I should be treated equally when it comes to my civil liberties, including my right to vote. If part of my money goes to pay my state representatives' paychecks, I believe it's my right to be able to choose who my representatives are, regardless of the fact that I am under 18.
A test on government knowledge would show that I'm capable of making an informed decision regarding who my representatives are.