When schools closed, online teaching was in weeks rather than years.
The speed hid how the result was.
Pupils with a quiet room and a laptop lost little ground.
Pupils sharing a phone with two fell behind by a year.
The gap did not close when the buildings reopened.
lessons help, but only those who attend them.
is lowest exactly where the loss was largest.
Online tools have kept a smaller and more useful role since.
is faster and a missed lesson can be watched again.
Nobody now claims a screen can replace a classroom.
The settled that argument by running the experiment.
What it did not settle is who pays to repair the damage.