The more classes you have already taken, the less impact each successive class' grade will have on the overall GPA. This makes it difficult to significantly raise (or lower!) a GPA during the senior year. I don't know all the variables at your school. For example, if they give more than 4 points for AP/honors classes, you could try for some of those classes. Of course, you want to do the best you can on whatever classes you take.
There are many ways to be accepted to a school other than "Automatically" with a GPA of 3.3. I would read the website/literature and try to determine what other characteristics the school is looking for. As an example, if leadership is important, try to become the leader of a student or community organization. If volunteer work is important, be active in such activities. Cultivate relationships with your teachers so hopefully you can get good letters of recommendation. See if you know anyone who went to that school, again, their letters would help! You want to be able to show the school how your diverse background would be a good fit for their school. Don't get so focused on the "3.3" that you neglect the other variables!