Learning continues throughout your entire life. Some students are choosing to just keep on educating themselves rather than enrol in formal universities. There are so many resources online now that it is quite possible to do this at an advanced level.
Given the rising costs of a university education, for some the real-world experience of work and travel combined with continuing to educate themselves is a better option.
Since 2012, a new free education movement has begun online with universities worldwide opening up courses online to huge audiences. Many of these are free and for most there are, as yet, no formal procedures for awarding credit but some have the option to do the course for free and then pay to sit exams if you wish. See the teenagers tab under Resources.
See also Uncollege although you don’t need to sign up in order to follow the principals of the idea which is outlined in Hacking your Education by Dale Stephens.