A Long Island driving instructor showed porn to three teenagers during a driving lesson, authorities said Sunday.

Mitchell Lerner, a 75-year-old Melville resident, was arrested Sunday at his home, Suffolk County police said in an alert.

Lerner was instructing three 16-year-olds in Smithtown on Dec. 22 when he showed them pornographic videos and photos on his cellphone, cops said. Police said they received a tip that led them to investigate Lerner’s actions.

Lerner was issued an appearance ticket, and his first court appearance was scheduled for an unspecified later date, authorities said. He was charged with three counts of child endangerment, a misdemeanor that carries a maximum one-year prison sentence.

Additionally, Lerner has been suspended from his job at Defensive Driving School in Central Islip, the school’s owner told Newsday.

Defensive Driving School sells itself as “Long Island’s premier driving school” and “has been helping Suffolk County residents improve their defensive driving skills, reduce their car insurance costs, and obtain their license for over 50 years,” according to its website. In addition to its main facility in Central Islip, the school has a classroom in Huntington Station.