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.
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Any mist or fog will clear during the morning to give another dry day with light winds and some sunny spells.
The bus was travelling along Hale Street when it collided with a number of stationary cars and a lamppost before crashing into Sainsburys.
Rescue teams dashed to Trinity Street in Coventry shortly after 6pm after the Stagecoach bus crashed into the front of the store.