ClassCalc.com

ClassCalc is a powerful graphing calculator app with a built-in lockdown browser that lets teachers lock students out of all outside distractions such as instagram, calls and texts, keeping students focused in class, and preventing cheating on tests. ClassCalc has 100k+ downloads on the App Store and Google Play, with 4.5 stars and hundreds of reviews and logs over two million calculations per month.

Website: https://classcalc.com