A 14-year-old innocent bystander was shot in the leg when a fight erupted outside a Staten Island high school Tuesday afternoon — as panicked students inside the building were warned, “This is not a drill!” cops and law-enforcement sources told The Post.

The wounded boy, who students said was a JV football player, was not the intended target when a gunman or gunmen wearing ski masks fired about eight gunshots near Tottenville High School in Huguenot at around 1:57 p.m., cops said.

“They believe he was running to get out of the way,” a police spokesman said.

As many as five people in ski masks were involved in the fight just outside the school, though it isn’t clear how many people fired shots, according to cops. A photo of the teen after he was shot showed cops treating him as he winced in pain with his right shoe on the street and his sock soaked in blood around the ankle.

An NYPD School Safety agent applied a tourniquet to the teen before EMS arrived. police said.

The boy was treated at Staten Island University Hospital and is in stable condition, cops said.

Tottenville was put into lockdown after the shooting.

“I was across the street, and I saw the kids come out of the car with ski masks,” a 13-year-old freshman girl told The Post. “One of them crouched down in a squat and pulled out his gun, and he shot at [a] kid. [The kid] fell to the ground, and another kid fell, but he wasn’t struck. He went under the car to protect himself.”

Inside the school, people were running and closing windows, yelling “Get down! It’s not a drill, get down!” said Sofia Shternfeld, a 14-year-old freshman.

“It was traumatizing,” she said. “And we all started shaking and calling our parents. We’re thinking, ‘Oh my God, what’s going to happen? Are they going to get inside? Are they going to get to our room?’ ”

The 13-year-old said she ran into the school for safety.

“I saw the whole thing. I literally can’t unsee it,” she said of the shooting. “They took us into a room, and we sheltered down. That’s when the announcement came on that said it’s not a drill and we need to stay quiet. It’s really scary to think that after all the drills we’ve done our whole entire lives, we actually went through that today.”

She texted her mother saying, “Don’t come to school, someone’s been shot,” her shaken mom said.

“I was late to pick her up. If I’d been here 5 minutes sooner, I would have picked her up before it happened,” her mom told The Post. “I think it’s crazy. At this point, it doesn’t matter where you are in the city, because it can happen anywhere, it really can. You want to protect your children from everything, and in certain situations, it’s hard to.”

Fayez Beshay, 22, who was arriving to pick up his freshman sister, railed against youth gun violence when he saw the aftermath of the shooting.

“I just don’t know when this is going to stop,” he said. “It could be someone else tomorrow. The access to guns is out of control. For kids to have access to guns and just shoot — and this was during dismissal when there were a lot of kids around — it’s just out of control.”

The shelter-in-place order was lifted by 3 p.m. and dismissal was underway, according to a tweet from New York State Assemblyman Mike Reilly, who represents the area where the school is located.

Additional reporting by Cayla Bamberger