I went to school a million years ago, but IIRC we kept our textbooks in the classroom until middle school (7th grade for me). Maybe one textbook might go home with math homework or an English project. For my kid, they would usually just send worksheets home; which is ok, but if you wanted to reference not on the sheet, too bad. Post-covid, there's a lot more dependence on google classroom with all that comes with it (but maybe that's also how the upper grades were working anyway)
E-readers with textbooks loaded could work, but hopefully the textbooks are tuned for the medium.
Anyway, isn't a heavy backpack a secret fitness program???
Like, maybe download wikipedia onto the device but don't give internet access. Let the device sync at school with required books and assignments.
Effectively, you could give kids a pocket library but that's the extent of what they should have.
It's essentially a notebook and a book reader.
You can take notes directly on the book if you use pdf (epubs can only have notes on the side).
I think that's the tech I want to see in school, no tablets please.