“Oh, my God, I set a kid on fire!”

That’s what a 10th-grade teacher shouted after her botched chemistry lab demonstration at the prestigious Upper West Side Beacon School left one boy looking “like a victim from a battlefield,” a new report reveals.

Chemistry teacher Anna Poole improperly poured explosive methanol from a gallon jug onto a still-burning experiment — then had no fire blanket or working extinguisher on hand to douse the boy as he writhed in agony, according to the report, issued Thursday by the Special Commissioner of Investigation for city schools.

“It’s very clear from the report that they conducted an experiment that they had been warned by the government was dangerous,” said Jeffrey Bloom, lawyer for badly burned Alonzo Yanes, 16.

“As a result, a gifted, talented young man has scars, physical and mental, that are going to be with him forever,” said the lawyer, noting that Yanes has remained out of school since the Jan. 2 accident and is still undergoing physical and psychiatric therapy.

He suffered second- and third-degree burns to his face, neck and torso. Moments after Yanes was set afire, another teacher ran in with a blanket and smothered the flames.

The school custodian “described the student’s left ear as being melted,” the report said.

As The Post revealed the day after the explosion, Poole — who wore goggles herself — gave her students no goggles or protective aprons and used no protective hood or barrier.

Student witnesses are quoted describing the badly burned student rolling on the floor in flames, screaming, “Help me!” and the shocked teacher saying, “Oh, my God, I set a kid on fire!”

They described “a fireball — like a blow torch — erupted and shot across the room.”

Julia Saltonstall, 16, was singed in the accident.

The report leaves it up to Schools Chancellor Carmen Fariña to determine what action should be taken against Poole.

A DOE spokesman said Poole will remain “reassigned while we carefully review the report and determine the appropriate action.”