A teenager suffered a dislocated jaw, cuts and bruises in an assault that took place in a town high street.
The incident took place on Wednesday 11 May 11 at about 7pm in the High Street in Daventry.
The 13-year-old was approached by three other teenagers, one of whom punched him to the floor.
Officers would like to speak to anyone who may have witnessed this incident or who may have any information regarding it.
Witnesses or anyone with information about this incident can contact police on 101 or Crimestoppers anonymously on 0800 555 111.