Head Start centers across the U.S. have received nearly $1 billion less in federal money compared with this time last year — and a lag in funding this week has caused some preschool classrooms for low-income children to close. The federal government has distributed $1.6 billion for Head Start from Jan. 1 through Tuesday, compared with $2.55 billion issued during the same period last year, according to the office of Sen. Patty Murray, D-Wash., which has been analyzing a federal database. Murray said the Trump administration had “slow-walked” funding appropriated by Congress.