This is an interesting article about the continued dominance of relatively expensive Texas Instruments graphing calculators in secondary education.
I still have (and periodically use) my TI-89. Even though my phone is vastly more capable, there’s something to be said for dedicated, optimized hardware keys for heavy use.
I relied on this calculator throughout high school, but when I got to college, calculators were simply not allowed for math tests. I thought I would hate this, but in reality it worked fine. I’m not sure why high school math courses don’t ban calculators for tests considering how many problems the TI calculators cause.
The article linked above quotes the founder of Desmos, which provides a free web tool with an accompanying iOS application that provides a lot of the functionality of a TI graphing calculator but with better interactivity. It’s worth playing around with!