Investigators described the teenager as being out of control.
A source close to the investigation told ABC7 News that the Mount Diablo High School student came back to school from a lunch break, drunk.
A Concord teen was tased by an officer at his high school - officials say he was out of control.— Amy Hollyfield (@amyhollyfield) February 20, 2015
Some students say it was obvious the teen was drunk.
"I saw the kid running and he looked pretty drunk. He couldn't walk straight or run straight," said one student.
A source says the student punched an officer and picked up a teacher up off the ground. Students watching the whole thing then saw an officer use his taser on the kid.
"It was like, whoa! I thought it was unnecessary. He could have tackled him. He was drunk. He didn't need to tase him," said Juan Aguilar, a student.
Parents, too, are wondering if that kind of force is appropriate on a high school campus.
"I believe they use whatever force is necessary for the safety of the other kids, but tasing? That's kind of extreme. They could have used physical force," said parent Sonya Sanchez.
"Our school resource officer is a wonderful member of our community he knows all the students and has a fabulous relationship with them and has been a great addition to our staff and we really like having him here," said Principal Liane Cisnowski.
She is standing by the officer, who is a member of the Concord Police Department. Having him on campus is new and she's grateful he's there.
"Our school had a school resource officer in the past, but due to budget cuts, we had to stop using a school resource officer. This year, though a collaboration with the police department and the school district, they returned the school resource officer to the three Concord high schools. And they have been such a blessing to us," she said.
The police and the principal said they can't comment on the situation because it is an open investigation.
The boy was treated at the hospital and then booked for assaulting an officer and resisting arrest.
The District Attorney will now decide if to press charges against the student.
School officials say the boy is a minor, so they have not released his name or any information about him.
No one was hurt in the incident.