Would you be in favor of letting 16 year olds being allowed to vote if they passed a fairly difficult voter competency test that 85% of adults had failed in when given? Let's assume they could study for the test all they want, take it once a day like their driver's permit test, and therefore had to be knowledgeable and/or at least have the dedication to keep studying and trying again and again until they passed. There could even be an additional restriction that they have had a job at some point. When they turn 18, they can simply vote.
I'd have to be solidly imposed on ever making the right to vote contingent on passing any kind of
“competency test”. No matter how good the intent, you know that any such test will eventually be abuse, in the manner that
“literacy tests” were abused in the past, to selectively deny voting rights in order to skew the results of the election.
As far as voting age, I see no benefit in lowering it to include people who do not yet have any real-life experience. If anything, I'd rather see it raised, so that voters are more likely to have had the experience of holding down a job, trying to support themselves and possibly a family, and having to bear the burden of taxes and regulations imposed by government. Young people, who do not yet have this experience, I think would be more likely to vote out of idealism for policies that are harmful to those of us who have to try to make a living in The Real World.