Missouri teens want to lower the voting age to 16 in local and school elections
(news.stlpublicradio.org)
The reason the system is so confusing right now is that laws are written for convenience and political gain. For example, Democrats in the US are currently pushing for younger people to have the right to vote because they will gain a political advantage.
i don't think this is really accurate. Democrats broadly don't care about lowering the voting age and it's not a signature plank for them--at most it's an incidental part of voting rights. mostly, the people pushing this are youth activists who also happen to be Democrats because young people are overwhelmingly a Democratic constituency.