A spokesman for Essex Police said: "We were called by colleagues at the ambulance service around 3.15pm with reports a girl had been stabbed at a school on Delaware Road, Shoebury.
"The girl was taken to hospital with injuries not believed to be serious.
"Officers arrived and arrested a 12-year-old girl on suspicion of causing grievous bodily harm.
"Enquiries are ongoing."What a lovely place England is becoming....