Lincoln police spokeswoman Katie Flood says Sarah Piccolo was found around 10 a.m. Tuesday in Woodson County, Kansas.
Officers there had been notified about someone with car trouble and found Piccolo. She's being held in a juvenile detention facility until she can be taken back to Lincoln.
The attack happened Monday morning inside a bathroom at the parochial school, which has nearly 1,100 students. 17 year old Ellen Kopetzky suffered injuries to her mouth and chin.
Police say she was also hit in the back of the head with a hammer.