The 15-year-old male pleaded guilty to one count of assault Thursday in provincial youth court in Summerside.
Court heard the incident, which took place last November outside Three Oaks Senior High School, was witnessed by a crowd of onlookers.
One of them videotaped the assault and posted it online.
Police say it was viewed more than two million times.
Court heard the tape shows the victim being punched repeatedly by the offender.
In addition to one year's probation, the youth must perform 25 hours of community work.
Because of his age, the boy cannot be named.