[Quoth]

It's complicated and depends of the technology platform and if the materials are adapted. Poor in primary/junior school.

This is not likely the best place to ask as the users here are predominately using ebooks for their own enjoyment.

Very many textbooks are not real ebooks (don't reflow), but PDF or other Print replica, i.e. electronic documents rather than ebooks.

Also colour is often needed, especially for juniors, which realistically means tablets. The iPads or Chromebooks dominate post-primary education in some countries and some schools have mandatory iPad or Chromebook systems.