A former Valley Stream Central High School District lacrosse coach pleaded guilty to sexual exploitation of a child in federal court on Thursday. Joseph Garofalo appeared in court in Central Islip and admitted to convincing a 13-year-old boy into sending him lewd pictures over social media. Prosecutors say he was an assistant lacrosse coach at Valley Stream at the time. The FBI says he has exploited more than 30 minors by blackmailing them into sending him sexually explicit photos and videos on social media platforms. Garafolo's defense attorney declined to speak to News 12 after his guilty plea. After the charges came to light, the school district sent a letter to the community stating it had been in contact with the FBI and assuring residents that none of the allegations against Garafolo involved students in the district. Garafalo is being held without bail and faces up to 30 years in prison when he is sentenced.