I guest there maybe a few very cheap $30 Google Android tablets and mini computers released in the past few years which are too slow for running school related apps like Word Processors and English Dictionaries.
But, it maybe difficult to find a newer Android tablet or mini pc which is too slow for running Android school related apps since slow Android devices wont have a lot of buyers. A lot of Android users are mobile gamers, play game console emulators, and watch a lot of HD video files, so a faster tablet or mini pc is important to them when buying an Android tablet or PC.
I think the Raspberry Pi 4 mini PC is now a lot faster than older versions of the $35 mini PC, so cheaper $35 PC are fast enough for Office and school work.