New Jersey will beef up police presence at schools across the state after a gunman killed 18 students and three adults at an elementary school in Texas on Tuesday, the Garden State’s top law enforcement official announced. Acting state Attorney General Matthew Platkin said he has directed the New Jersey State Police and all 21 county prosecutors in the state to “increase law enforcement presence at schools throughout New Jersey effective immediately.” Platkin said the State Police will increase its presence at schools where troopers are the primary law enforcement, while county prosecutors wil…