Do you have any refs for the TI83 being mandatory in US high schools? A quick google search puts your post at the top and nothing too relevant anywhere else. I graduated from a public HS less than ten years ago, and I used the far superior HP-48G throughout the entire thing :) I never took math classes from my HS, but I do remember my friends who were taking HS courses having an assortment of TI81 - TI89 calcs.