Most London children were evacuated through their schools. Altogether 827,000 school children were evacuated along with 103,000 teachers and helpers. 524,000 children under the school age went with their mothers. 12,000 pregnant women also left the city to protect their unborn children.

This government notice was posted in schools telling parents about evacuation:

Government Evacuation Scheme.

The government have ordered evacuation of school children. If your children are registered for evacuation, send them to their assembly point at once.
If your children are not registered and you wish them to be evacuated, the teachers or school keeper will help you.
If you do not wish your children to be evacuated you must not send them to school until further notice.
Posters notifying the arrival of parties in the country will be displayed at the schools at which the children assembled for evacuation.

E. M. Rich. Education Officer L.C.C.

(L.C.C. stands for the London County Council. This was the local authority that ran all the schools in London).

Entire schools were evacuated, along with teachers and helpers, and many evacuees experienced lessons that were very different from the ones they were used to in London. This page has a number of examples of London schoolchildren and the things they did when they were evacuated.