The mother of a teen stabbed to death by a classmate inside a Bronx high school classroom said after court Thursday that she doesn’t buy the killer’s claim that he can’t remember the stabbing.

Abel Cedeno, 19, had just insisted on the witness stand that he remembers being bullied and punched by his classmates on that late September, 2017 morning in history class, but can’t remember the stabbing itself.

Louna Dennis, mother of 15-year-old victim Matthew McCree, called Cedeno’s selective forgetting convenient.

“What I didn’t understand is, he don’t remember at no point in time when he used the knife — but however he remembers when he was being hit,” Dennis told The Post.

Cedeno took the stand in his own defense on Thursday to explain his claim that he was trying to protect himself when he killed McCree and seriously injured another student, Ariane LaBoy, then 16, inside the Urban Assembly School for Wildlife Conservation on Mohegan Avenue in Tremont.

The two were throwing punches at him and a third kid was punching him from behind, he testified.

“I don’t know the specific moment when the blade entered their bodies,” Abel Cedeno chillingly admitted on the last day of testimony for his non-jury manslaughter trial.

He snapped that day after years of homophobic bullying, Cedeno insisted.

When prosecutor Nancy Borko asked on cross examination why he didn’t just leave the classroom when he had the chance, Cedeno told her, “When you fear for your life, you can’t move.”

How many times before, the prosecutor then asked, had he feared for his life “with a knife in your hand and the blade out?”

Cedeno answered, “That was the first time.”

McCree’s mom wasn’t buying that either.

“You said you were standing by the door, you had enough time, more than enough time (to leave), if you fear for your life,” she said after court.

“No one was blocking you so why didn’t you just walk out through the door?”

The teen testified on direct that after the stabbing, he fibbed to cops that he was bisexual, instead of telling the truth — that he was gay. His parents were there and would have frowned on the truth, he said.

“I told (the detective) I was bisexual because as I said before, it is something to be ashamed of, and if I am half gay it would be easier to be accepted,” Cedeno testified.

He also revealed that his guidance counselor had wanted to have an intervention about the bullying but Cedeno told him no, “because it would make it worse.”

He explained, “They would call me a snitch.”

Former New York State Sen. Tom Duane, who is openly gay, attended Cedeno’s testimony Thursday and spoke to The Post afterward.

“It’s heart breaking,” said Duane, who was instrumental in the passing of the anti-bullying Dignity For All Students Act in 2010.

“The Department of Education has nothing in place to protect everybody. Schools should be a safe place for everybody.”

Closing arguments are set for Friday.