A retired Hamilton high school teacher admitted last week to having sexual conduct with a female student over 20 years ago, the Mercer County Prosecutor’s Office said. Joseph DePuglio, 77, of Ewing, entered the pretrial intervention program, known as PTI, on an endangering the welfare of a child charge as part of a plea agreement with the Mercer prosecutor’s office. During the plea hearing on April 18, DePuglio admitted to engaging in sexual conduct with a Steinert High School student between 1998 and 2000, the office said. DePuglio taught physics at Steinert before retiring in 2008 after 40 y…