The girl fought back, yelling and then kicking the suspect in the groin. She ran away and hid behind a bush until she felt safe.
Police have released a sketch of the suspect. The suspect is described as a black male in his 50s, with salt-and-pepper hair and a one-inch scar on his left cheek underneath his eye.
Police said there will be extra patrols around Lynwood Middle School on Friday.
Anyone with information is urged to call the L.A. County Sheriff's Century station at (323) 568-4911.