<p>Yes you should take those classes, but not at the expense of college requirements and alternate education. IOW, don’t skimp out and only do art. You may find yourself needing to go to a state university and not a private college, in which case you still need to look good all around to hold good chances. I have a friend who is basically having 5 classes his senior year, three of them art. He is entirely banking his schedule on the fact that he will get into CCA, one of the best art schools in California, maybe even the nation. I don’t think that’s necesarily a bad thing, it just looks lazy to more ‘traditional’ schools. Then again I’m all for trying your hardest in education, so I’m morally obliged to tell you to do the most you can. 
If you have at least a B average I’d say you’re good. If you specify your major as designing and let colleges know in your application, they will look more toward that end of things. Look around for some art competitions, art camps or anything like that. Volunteer at a museum or try and find an internship at a small designing place around. There are plenty of specific things you can do to give you that special edge.</p>