Voting age

I think 18 is a good general age, but there should be exceptions. I know plenty of well informed and responsible teenagers (under 18) who have the knowledge and opinions to be able to vote, but they can't because they aren't 18 yet. I think it is unfair to them because they would be better voters than many of the adults in this country who vote based on a party, and not based on who is a more fitting candidate. There should be a voting test for people under 18, and if they pass it, then they can vote.