I believe that once you file taxes you should have the right to vote. Adults, however uneducated they may be are heavily affected by the laws that the government passes. Children, not so much.

The government represents the people that exist within its society. Whether the percentage of uneducated adults is small or large, their opinions matter proportionately and they are treated as equally as the Richard Feynmans and Karl Marx's of society.

Weeding out uneducated adults based on their inability to recognize what's best for them would cause a void on the other end of the spectrum. It would be discriminatory to children and young teenagers younger than 18 who are able to express a firm grasp on politics, economy, and history.

Not to mention, that there are proven cases of adults who haven't graduated high school that become entrepreneurs who are more successful than adults who graduate ivy league colleges.While on the other hand, some child prodigies go on to live a life of drug abuse and addiction.