A woman apparently upset over the treatment of her children by other students rammed her minivan into the front of the Huey Elementary School (search) in West Philadelphia this morning.

No children were injured, but a bus attendant standing inside the school was slightly injured when the van with the woman and three children crashed into the front door of the school, about 50 feet from the street.

There was no major damage to the vehicle or the school building and little more than a bumper mark on the door of the school.

School officials say the woman had been complaining that her children were being picked on by other students since being transferred to Huey Elementary in December.

Investigators say they found signs in the van protesting the children's treatment. Authorities say the woman had threatened to drive into the school on Monday, but police were notified and an incident was averted then.

The three children, two boys and one girl, were taken to a nearby hospital to be checked out.

The mother is in police custody and is being questioned.