After a spike in violence at a high school in the Bronx, schools Chancellor Carmen Fariña became personally involved in the solution, which included getting cellphones back out of the school. NY1's Lindsey Christ filed the following report.

Grainy security footage from December shows a violent fight, one of many erupting outside of the Lehman High School campus this school year.

"My office is three blocks away, so I can only tell you, it was difficult on the streets," said City Councilman James Vacca of the Bronx.

Administrators say Lehman, one of the city's most troubled high school buildings, experienced a spike in violence after Mayor Bill de Blasio lifted the cellphone ban in schools last year. Students began using their phones inside the building to arrange the fights. including repeadedly pulling the fire alarms, causing all 3,000 teenagers to pour onto the streets, where the beatdowns would occur.

"The business community reached out to me, many residents reached out to me, and we became increasingly concerned," Vacca said.

Six weeks ago, Chancellor Carmen Fariña became personally involved, visiting Lehman, setting swift deadlines for action and dispatching her deputy for security to oversee the turnaround.   

"We've just really tried to change the culture and what's happening in the building," said Maria Herrera, principal of Renaissance High School for Musical Theater Technology at the Lehman campus.

Fariña invited us to walk the building with her Monday to see how the six high schools that share the campus are trying to turn things around.

The biggest change? The schools began collecting cellphones. Students now drop phones into mailbox-like containers and get them back at the end of last period.

"The violence kind of went down a little bit because before with the phones, I think people was like, 'Oh this person is right here and we could go get him right now,' and they would meet up and go jump somebody like that," said one student.

The police also arrested a student for pulling a fire alarm.

"It hasn't happened recently," said one student. "I think people are kind of scared now."

The principals of the six schools at Lehman hired a security director and began meeting more frequently to address common problems, meetings that led to the new no-phone policy. The principals also established a campus-wide student council and are trying to get parents more involved in the schools.

The chancellor says she wants other schools to visit Lehman to learn from their experience..

"I would think any school that sees themselves headed in this direction will have a way to preempt that," Fariña said.

Owners of businesses around the school say they've noticed the change. At Lehman, a lesson learned.