Right. So, you're going to have a huge youth problem on your hands of uneducated and more often than not aggressive teenagers with poor prospects for the future and poor willingness to get themselves through school by choice.
Even in well run societies, youth culture can be found as a driving factor in vandalism and assaults - and I say that as a card-carrying punk rebel. It's going to happen, and as beautiful as a free young person is, there's going to be a lack of control over the damage it has to people who just want to be safe. In your society, this will only be more problematic.
IN ADDITION TO THIS, lack of universal education stratifies your society. A class of people who have no problem pressuring and forcing their kids through education by any means necessary will hog up opportunities denied to the children who experience no such pressure until they're at working age anyway. They lack the work ethic to use adult education efficiently, and even the most eager to turn themselves around after youth will never really catch up. The layers this creates in society will drive resentment, hatred, and possibly even bloodshed.
By the way, none of this is speculation. This is based entirely on historical examples of places that have gone down this route in the past.
Great leader, your thoughts? Your reaction? Your policy?