I'm inclined to think that the medieval trivium (logic, grammar, rhetoric) is a good foundation for education in general. Logic seems to go particularly underutilized, although I have memories of various 'critical thinking' drills starting from middle school onwards. The corresponding 'quadrivium', with its heavy basis in mathematics, is also useful and provides plenty of opportunities for mental stimulation.
If we think of this in terms of goal-based education, the primary goal is to learn how to think and acquire knowledge, which is a reasonable preparation for career based education. To be fair, the potential education a person has access to at the moment is much better than it's ever been, and attempts are made on much broader segments of the populace. On the other hand, a bad education can cause more damage than neglect... or a constant bombardment of anti-rational, anti-intellectual ideas in society.