Five boys aged between 12 and 15 were arrested after fleeing with the teenager's designer bag at around 6.30pm on Saturday. Four were found hiding in a bush and another climbing a fence.
Members of the public helped officers trying to find the boys by directing them to Two Woods Lane.
Police were called to reports of a robbery involving a knife. No weapon was recovered and West Midlands Police said the investigation was ongoing.
A force spokesman said: "We were alerted by security staff who saw what happened and made our way to the scene.
"On arrival the boys ran off, but we were pointed in the direction of Two Woods Lane by some very helpful people who had witnessed the incident.
"One boy was found climbing a fence, another four were found hiding in a bush.
"All five boys, the youngest aged 12 and the oldest aged 15, were arrested on suspicion of robbery. They remain in police custody this afternoon (Sunday)."