Now you're changing the argument entirely, and not in a very promising direction for you. If it's a question of knowledgeability, you've just undermined your entire scheme to give 13 year olds the vote.In fairness, that was proposed by jlgreco, and I just wanted to use that suggestion to move toward a more practicable discussion of the de facto disenfranchisement of younger voters by the two-party system, higher turnout among older voters, etc.
A possibility I would like to consider for discussion is a multi-tiered legal system in which every ~25 years the new generation starts from scratch with a new set of laws, limited only by a small set of human rights guidelines. People can then opt into whichever generation's set of laws they want, with the ability to switch tiers every year or two, but you can only vote in the tier for your age group.
It's not a fully formed idea and I"m sure one could poke lots of holes in it, but I still think that it would be interesting to discuss in another context (this thread's already long enough that this comment is only an inch wide on the article page).