Do 16 year old's pay taxes? Only the ones that work, which might be 50% but I think it's even lower than that. Also although they might be more engaged than some adults, that's mostly due to the fact that they civics is an important part of most curriculum's especially social sciences. I remember most of my high school (as I am only 20), I remember I had 4 teachers that were strong NDP supporters one of which ran for the NDP, and then most of the other teachers were either apathetic, or centrist. Throughout my whole High School I only remember having 2 staunchly conservative teachers. Not only that but High School curriculum's, I remember watching two Michael Moore films (Supersize Me in health, and Bowling for Columbine in Social Studies), Al Gore's An Inconvenient Truth in science, but would we be able to watch Bloodmoney in health- no, would we be able to watch Fracknation in science- no. It's a miracle I survived High School as a conservative, although I was more a libertarian during HS. So don't pretend this isn't a tactic to support your own political ideology.
Most people under the age of 30 if they have political beliefs, they lean more left. Now I disagree with raising the voting age too even though it would help my own party. Raising it to 30, there's no reason besides your own political motives. Raising it to 25 (or would have 21) is because that's the time scientists say your brain stops developing, but just because your brain is still developing doesn't mean you aren't old enough to form an opinion.
I like the voting age being 18, if you're old enough to die for your country, you're old enough to elect leaders that will send you there. People are allowed to have differing opinions that's part of democracy, just the reason why we have age related laws is because people believe that you are not prepared or not informed enough to take part in certain actions, in the case of voting, I don't believe 16 year olds are exposed to enough alternative opinions.