Police say at least four others are being sought in connection with the attack.
The incident happened at around 12:50 p.m. Friday in the schoolyard of Julia Ward Howe Elementary School, located along the 5800 block of north 13th street.
Philadelphia School District spokesman Fernando Gallard tells Action News the older students attacked ten 4th and 5th graders with bats.
Though the students were hit in the heads and stomachs, the district says the injuries were minor; the students were tended to by the school nurse.
School officials say they have no idea what prompted the attack. Two adults were monitoring the younger students on the yard at the time of the attack.
One ushered dozens of the students inside while the other called 911 and pursued the attackers on foot.
School officials say police responded promptly and caught the three that are in custody.
A letter was sent home to parents explaining what happened and school officials vow to get to the bottom of this attack.