I used to do a similar thing when I was in middle/high school. I do not consider myself to be a great writer, but when I was in school, I did very well for what my teachers expected at my grade level (I liked to read a lot). Most teachers I had wanted us to write essays or stories and then spend the next few classes fixing up our rough drafts into a final draft. I knew my first rough drafts were better than most other students’ final drafts so I would purposely put in spelling and grammar issues and maybe spend a few sentences off topic. Those would be the things I fixed to create my final draft. Doing that gave me more time to focus on subjects I had a harder time with.