After Germantown closed, he said, "I wanted to follow the kids here. . . . A lot of them are trying to find themselves in the midst of all this chaos."
Dontae Angus, a senior who transferred from Germantown, shook Custis' hand on the way into school and nodded in assent to the officer's signature question: "You good?"
Angus, 18, a tackle on the MLK Cougars football team, said the rivalry between the schools had not caused any problems for him during preseason practices.
"I'm just coming here to learn," said Tenele Moore, another Germantown student entering 12th grade. "I feel good."
The majority of the school's more than 1,000 students are, like Moore, focused on learning, principal William Wade said, adding that he believes the media attention and adult anxiety about gang violence are overblown.
"The only issue is getting to higher levels in the classroom," said Wade, who took over at MLK three years ago. "Literacy and numeracy, that's my battle."
He acknowledged, however, that to maintain students' safety, the school needs the 14th Police District to post officers outside the building at times, especially at the end of the day. Custis' staff of 10 patrols hallways and cafeterias constantly throughout the day.
"Of course," Wade said, "you have hiccups any time you have large groups."
One of those hiccups occurred about 11 a.m. in a stairwell where a ninth grader was jumped by several older students. Although the fight was caught on a security camera, it ended so quickly that the attackers could not be easily identified.
Called into Custis' office, the victim refused to speak.
"I'm not telling on nobody," he said.
"You all got this whole thing of no snitching," Custis sighed. "That's the most idiotic thing."
While the boy's parents were called to take him home, Custis' staff gathered enough information to haul in a few of the most likely suspects.
"I can't have this, fellas," he told them.
The two boys, cocky at first, began to fidget.
"You keep this up and one day, you are all going to have a big ol' memorial for you on the street somewhere with teddy bears and balloons," he said.
He then asked the boys to shake hands on a promise that they would not get into any more fights.
"You're here about your education," he said. "Anything else, you're breaking your word. The next move is, you're gone."
In exchange for their cooperation, he promised tangible rewards, among them pizza.
"Whatever works," he said, "if it keeps my 180 days quiet."
Contact Melissa Dribben at 215 854 2590 or firstname.lastname@example.org or @dribbenonphilly.