I ran into that problem in the later years. Elementary and middle-school art were just fine for me. You were given a subject and told to draw it (or paint it, whatever), you did what you did, and turned it in. Sometimes you would be given a medium, like tempera or lenoleum, and told to do whatever you wanted to do with it. That was cool stuff.
Then I got into high school, and took "Advanced Drawing". Suddenly, we were doing much less of the "here's a subject, knock yourself out" line, and started doing some "here's a particular style of drawing, make a drawing using this technique". That irked me. If you didn't get the technique right - if it just didn't "work" for you - you got a nice LOW grade on it. "You didn't learn the appropriate concepts". Well, that's not true - I knew the appropriate concepts behind the technique; I just despised them.
The problem was worse when I took painting. "Today, we're going to learn to paint in the Monet style". Well, I like Monet's (van Gogh's, Picasso's) paintings, and the technique is cute, but I am not particularly interested in learning to paint like him, nor do I plan on using his technique anytime in my life, ever. And of course, you could be a living legend at the technique you like the most - but if the class even covers that technique, it's only one A in a sea of Cs and Ds you earned because you didn't try to hard enough to paint like Monet (van Gogh, Picasso) on those days. In my senior year, since I (barely) passed the advanced painting and drawing classes, I was able to take "Independent Studio", which rocked. The class was simple - do two "large" projects and three "small" ones. You have all year. Use any medium, any subject. I made two large oil paintings, two drawings, and a ceramic ashtray. There were some days I sat in there and just talked with my friends. The teacher was available for help if needed, but mostly sat and chatted with us.
There are classes like Independent Studio at my college...but just like in high school, you've got to "earn the right" to take them by schlepping through all the garbage...presumably, by learning how to paint like Monet...again. No thanks. I've learned you don't have to be taking an art class to submit work for gallery shows or competitions there, which is good.