Education should not be mandatory, but making it through "high school" grants you the right to vote perhaps. If it's opt-in, then you have parents and children who want to be there, and you can exit any time. 8th grade education would be as rigorous as today's "high school" and by the time they're graduating the "new high school" (old 1930s standards) you'd have most of a 2nd language, pre-calculus, the main body of Western literature, and could write & debate as befits a citizen we'd want to be proud of.