There's a lot of countries where it's not normal to keep going to school until you are 18.

In New Zealand, you can leave school when you're 16 and start an apprenticeship. I think that by 16, most people will know if they're definitely not going to be going to university, and I think that 11 years of schooling is enough to set people up with the basics for life. It's the point where (at least in New Zealand) you start specialising, picking specific subjects that are going to help you with, or be required for, university