I'd say it doesn't cost you anything to learn to code, Getting a formal introduction to it in school is a great addition to your education as it surrounds you with other people interested in it and you will have mentors that you can learn from side-by-side.

You can certainly advance yourself further under your own efforts outside of class too.

If you've got an idea that you want to build, I'd certainly spec out the idea as much as you can first, even if it's just pen & paper to start with. features, ideas, demographic/target market. Build up a swipe file with ideas, images, text of things that will be useful in projects in future.