At this point in 2019, with such cheap computation, the school calculator lines are being sold as much on what they don't do as what they do.
Around 1994 or 1995, I had an HP-48G calculator, a real scientific programmable calculator meant for engineers and scientists, where the rest of the class had the TI line of school calculators. The HP-48G could do most of the integration problems we had, symbolically. IIRC, there were a few high school integration problems it couldn't do, but it did a pretty good job. And it was a bottom-of-the-line, stuck on an embedded system computer algebra system even at the time. It only goes up from there.
You don't want the students to be rolling into the SATs with computer algebra systems that can solve all the problems on the exam. This is also why they can't, for instance, bring in an Android system running the TI in emulation; it's not about doing what the TI calculator can do, it's about not being able to reach Wolfram Alpha.
The model restrictions are about the test authors being sure they know what's up.
(On the plus side, if you want to teach students how to use computers well, leave them a loophole where they can bring in their android phones, install a linux app, run Sage[1] from within that, and figure out how to use it to solve their high school calculus problems. You will learn something students, one way or another!)
[1]: http://doc.sagemath.org/html/en/reference/calculus/sage/symb...