As a teacher myself, I will always advice young people to go to school. Though I imagine it differs on the quality of education in your country.

I live in the Netherlands and here it's quite good overall. It's no Ivy League and there are plenty of exceptions but overall any technical study here is a good study.

I also teach at a small school (220 software engineering students) so I actually know my students and what generally need to get ahead.

But my main reasons for actually doing a study instead of going the self-taught route:

1. You spend +/- 4 years in presence of peers that are more or less in the same life phase as you are. You will make friends for life.
2. Companies value a diploma. Good for you that you landed a job on your 19th. Just wait until your 25, wanna switch jobs and don't even get to the second round of any application process because your CV does not list a diploma. This might change in the future but not for the next 5-10 years.
3. You will learn foundational stuff about most thing IT-related. Some things you'll never use. Some thing you'll use unknowingly every single day
4. It teaches discipline without major impact on your life if you fail something. OK, you failed a course. So what? Take it next year and take the time to do a side-project or internship during your study delays. It will teach you some life lessons without it costing you a job or your life savings, and you get some extra time to learn as well!
5. Retirement age by the time you retire will be 75. There's plenty of time to work. Why not spend 4 years with peers in a relatively safe and fun environment first?

TL;DR - small schools are actually fun, attend one