Dissident Republicans are being blamed for the killing during rioting in the city.
One in five teachers buys lesson materials once a week, a survey by the NASUWT union suggests.
Police rest days are cancelled as more than 1,000 officers are deployed in London.
A dozen named groups and individuals will be purged from the social network, it said.
Milly and Toby Savill were on Santorini when the buggy they were in fell into a ravine.