I am also in 10th grade and have the same classed as you. I have the 83 >and I think it is great and it does everything you need. I recomend the >85 however, because it has a very helpful conversion function, and it is >the highest allowed on the PSAT ans SAT tests. THIS IS A EASY QUESTION. A TI-86 if perfect, becuase it will last you though this year and the next. GET AN 86!!!