<p>What's the difference? I think that 10 is for 10th graders and under, and 12 is for 12th graders and under, so how do you know which one you should take?</p>
<p>Well that's basically it... But if you're in precal + (or maybe even alg II/trig +) you might want to consider taking AMC 12. The cut-off score for AIME is lower on the AMC 12 (granted it is harder) but if your up for the challenge it's a good thing to do especially for practice later on. Two years ago (I was in precal- 10th grade) I took both tests and I made AIME on the AMC 12 but not on the AMC 10. Of course, I took the AMC 10 first and I hadn't taken the test before so that might have helped... but still. Do whichever you think you have a better shot with.</p>