Schools in South Brooklyn that locked down after Tuesday’s subway attack were back to business Wednesday — but attendance at some was way down as worried students opted to say home.

“People were nervous. There was not a lot of people that showed up to school today,” said Areli, a student at John Jay School for Law in District 15, which includes Park Slope and Sunset Park. “It was just quiet.”

Attendance was way down at many of the schools near the scene of Wednesday’s subway attack, in which 29 were injured, including Sunset Park High School and P.S. 371, where just 39% showed up — less than half the rate of last school year at 77%, according to DOE data.

That number was 55% at P.S. 371, compared to 73% last year. At John Jay School for Law, it was 67%.

“We could’ve been on that train that morning,” said Areli. “It could have been us, or one of my friends, or people I know in general.”

The 17-year-old opted to walk home for 30 minutes on Tuesday, instead of train, and the next day commuted to school by bus. She said she felt safe at school but had concerns outside its four walls.

Other kids in the area echoed her concerns about the commute.

“I didn’t see a lot of kids in school today,” said Lesly, a junior at Millennium Brooklyn in Park Slope, though she added there weren’t as many absences there as she thought there could be.

“Taking the train, honestly, was nerve-wracking,” she said. “I kept looking around. I was more aware than usual.”

Sunset Park parent Vincent Lu, who sits on the district’s Community Education Council, an advisory board mostly comprised of parents, was overall impressed with his family’s school’s response.

He said there’s some “room for improvement,” but that he wants to see more collaborative work with other city agencies.

“I don’t think it can be done by schools alone,” Lu said.