Lily Smith/The Register/USA Today Network/Reuters via CNN NewsourceBy Michelle Watson(CNN) — Ian Roberts, the leader of Des Moines’ schools who was detained by immigration agents last week, is resigning, his lawyer said Tuesday. “We will today be sending a letter to the Des Moines school board authorized by Dr. Roberts to resign his position as the superintendent of Des Moines public schools,” his attorney Alfredo Parrish said during a news conference. “Out of concern for his 30,000 students, Dr. Roberts does not want to distract the Board, educators, and staff from focusing on educating DMPS’s students,” the letter said. He was placed on paid and then unpaid leave by the Des Moines School Board. Justice Department opens investigationThe Justice Department opened a civil rights investigation into Des Moines Public Schools (DMPS) over its employment practices, the agency said in a news release Tuesday.