Carl Williams, Headteacher at Moreton School in Wolverhampton, has described an incident in which 20 pupils were jabbed with a diabetic testing needle as "frightening".
Some of the children have been taken to hospital for hepatitis jabs as a precaution.
An 11-year-old boy has been arrested.
More top news
Snowfall will begin to ease and become largely confined to higher ground.
Cold with sunny spells and more snow on the way.
A top Tory councillor has offered to compile charity joke book, after being caught sending a string of sexually explicit and racist emails.