It's important to plan ahead - "get ahead of the game" whether planning for SAT/ACT or planning for this coming Fall, 2012.
Most parents and students wait till they get an "unexpected bad grade" - then REACT. A tutor can help things turnaround at that point - but what about your other classes - do you ignore those to catch up? This is not a good situation. Pressure packed. If this happens to be the semester they are preparing and taking the SAT or ACT, or they have to prepare to take an AP exam - even more pressure.
I am thinking primarily in terms of math/science. If your student can start a tough math or science course in the fall having already mastered several key fundamentals of that course, it will give them confidence, relieve stress, and move them to a higher level of understanding.
Also plan ahead carefully in class selection. You want a strong high school resume, but not at the expense of a significant drop in grades. My own daughter took statistics this year as the "class for average math students" (vs. Calculus) and guess what: "Stats" is a tough course! She was surprised and had her own bad grade but with a built-in tutor re-took a test and took it from F to A.
This fall hire a tutor - just 4-8 sessions - to both prepare your student for the Fall and "reinforce" key skills and understanding. Work on organization, time management, teacher interaction, test preparation and study skills.
Get ahead of the game. Don't get into a crisis mode right in the middle of a very busy semester. Even now with our kids' super busy summers, there is some down time - use it wisely! BE PROACTIVE!