This is what I did towards the end of high school. I did no revision outside of class (and did most of my homework in other classes), instead spending my time at home coding or socializing. I still took an A* in math and As in sciences and a few other subjects, with the remainders as Bs (except for Ds in woodwork and religion!) .. Didn't harm my future prospects at all and the coding practice helped a ton in getting my first couple of jobs.