An 11-year-old boy will need surgery to have pieces of brick removed from his eye after teenagers hurled the missile at him.
The boy was walking with two friends near Thorntree Cemetery in Middlesbrough on Thursday evening.
Police said a group of teenagers threw a piece of brick that hit the 11-year-old directly in the eye.
He was treated in hospital for 90% damage to his cornea and pieces of brick were embedded in his eye.
Police said the group was aged between 13 and 15 and were wearing tracksuits and hoodies.