What about cutting off just mobile data + school wifi? Everybody with wifi or a network connection elsewhere would be just fine. Still extreme, but dramatically less disruptive.
Plausibly you could limit this further, to block data only on phone masts near schools.
Still an ridiculous measure, but I'm really surprised that they've taken the most extreme measure possible instead of trying to limit the fallout at least a little bit. It's not like nobody is using it - https://data.worldbank.org/indicator/IT.NET.USER.ZS?location... shows that by 2017 more than 1/3 of Syrians had internet access, and rapidly increasing.