A Bronx judge didn’t buy a teen’s claim that he stabbed a classmate to death over constant bullying because he is gay — and found him guilty on all counts Monday.

Abel Cedeno, 19, had requested a non-jury trial, meaning the judge decided his fate on first-degree charges of manslaughter and assault and fourth-degree criminal possession of a weapon.

When Cedeno’s lawyer asked for bail for his client until sentencing in September, Justice Michael Gross, retorted, “The presumption of innocence no longer applies to Mr. Cedeno’’ and ordered him remanded.

“This was a possible and foreseeable outcome,’’ Gross added of Cedeno’s actions.

The teen had plunged a switchblade into the chest of Matthew McCree, a fellow student at the Urban Assembly School for Wildlife Conservation, in September 2017 after the victim and a male pal allegedly tossed a ball of paper or pen at him and three started fighting.

Cedeno, who also seriously wounded the friend, has since come out as bisexual.

“I love you, Papi!” Cedeno’s tearful mother yelled to her son as he was led away in handcuffs after the verdict.

The teen replied, “I love you, too.’’

Cedeno will be sentenced Sept. 10 and faces up to 25 years behind bars on each of the top two counts alone.

“What does my heart tell me? That the judge did the right thing with that verdict,’’ said McCree’s mom, Louna Dennis, after the verdict.

“What was in my heart? That praise be to God for this outcome, for the prayers and everything that all my family and church has been doing for me,’’ she added.

At trial, Cedeno said he didn’t remember the actual moment he killed the 15-year-old McCree.

He said he just whipped out his knife n the hopes that “people would be afraid and not come near me’’ but that McCree charged him and he stabbed him in self-defense.

As Judge Michael Gross read his verdict, McCree’s family gave a hushed cheer from one side of the courtroom, while Cedeno’s camp on the other side started weeping.

The killer’s lawyer, Christopher Lynn, asked the judge to allow his client to stay out on bail until sentencing.

“He’s certainly not going anywhere, Judge. He has no resources. He’s been a resident of this city and state his whole life,” Lynn said.

But the judge replied, “The presumption of innocence no longer applies to Mr. Cedeno” and ordered him remanded.

Bronx DA Darcel Clark said in a statement Monday, “In a matter of seconds, the defendant took out his knife and stabbed two students in front of a crowded classroom.”

The two victims “did not know and did not socialize with the defendant prior to the incident,’’ she said.

“The incident has forever traumatized the young students and school faculty who watched in horror the violence that unfolded that morning.”