I’m the author of a system called Adventuron Classroom, which is an online text adventure authoring system.
NOTE: The game editor currently requires a non-mobile client, so if opening the editor via and Android or iOS mobile devices, you will be informed you need to log in via a laptop or desktop computer.
Anyway, Adventuron should be fast (once initially loaded), as it doesn’t go back and forward to the server during use, and it caches in the browser after accessing the first time, so it should be fine for a whole classroom with limited bandwidth.
It runs fine on a Chromebook, and is expressly developed to be used in classrooms (has an inbuilt tutorial). Games, once developed, can be exported as a single file html files with no external dependencies. Games will run on desktop, tablet and mobile platforms.
I recently started a game-jam here:
Do try out Adventuron, and see if it fits your needs. It’s nowhere near as advanced as Inform but for beginner level text adventures, it’s perfectly adequete, and the online tooling should fit low bandwidth / high latency scenarios (once cached).