A school of about 50 sand sharks was spotted off a Long Island beach Tuesday morning — just hours after a girl was bitten at the same beach and nearby a boy suffered injuries in the first confirmed shark attack of the season.

The sharks were seen schooling about 200 yards off Robert Moses Beach around 8 a.m. before the beaches opened for the busy Fourth of July holiday as staff conducted a precautionary check of the waters.

“There were about 50 sand sharks that we saw,” Long Island Parks Regional Director George Gorman told The Post.

“Obviously, we did not open for swimming at 8 o’clock when lifeguards came on duty.”

Gorman said staff monitored the school of sharks, also known as sand tiger sharks, with surveillance drones for about an hour and a half before they determined the beaches were safe and opened for the day around 9:30 a.m.

“Sand sharks are very common off of Long Island,” Gorman said, noting that the large school was not something out of the ordinary, but that “individuals are more common.”

The shark sightings come after a 15-year-old girl swimming off Robert Moses Beach around 1:45 p.m. Monday said something bit her leg.

She suffered small puncture wounds, but it remains unconfirmed whether she was munched on by a shark or another marine animal.

Gorman said he didn’t want to speculate on what might’ve bitten the girl as there were no witnesses.

Hours later, and just three miles west on Fire Island, a 15-year-old boy was surfing at Kismet Beach when a shark took a bite at his feet and left him with puncture wounds in his ankle and toes.

He swam to shore and a bystander helped him as they waited for officers from the county Marine Bureau to arrive.

The boy was taken to Good Samaritan University Hospital in West Islip with his ankle and toes intact, Suffolk County police said.

Authorities confirmed the boy was attacked by a shark of some kind.

Despite their frightening ragged-toothed appearance, sand sharks are generally docile creatures.

On the rare occasion they do bite humans, it is usually because hands or feet were mistaken for the bunker or other baitfish they feed on. When attacks do occur on Long Island, it is not uncommon for them to be from sand sharks.

The confirmed Fire Island bite was the first of the 2023 summer season on Long Island following eight reported attacks last year — an unusually high number which resulted in Gov. Kathy Hochul bolstering surveillance capabilities.

Before the season kicked off in May, Hochul announced that 10 new shark-spotting drones had been purchased to help Long Island police and park officials monitor the beaches from the air.

Gorman said those drones had already been put to work in this week’s operations, and that more lifeguards and park staff were being certified to operate them by the day.

Asked whether he thought beachgoers should expect another year of increased shark activity, Gorman said he hoped not, and that beaches were well equipped to maintain safety.

“We’re hoping it will not be the same pattern,” he said. “That’s one of the reason that we have all the advanced surveying and monitoring that we put in place.”