THE BRONX - Today marked the first day of school for the city's public school students, but it wasn't without safety and transportation problems. With one school in particular, P.S. 51, the Department of Education found elevated levels of toxins over the summer. The students have since been moved to a new building, more than two miles away in the Crotona neighborhood. Parents took their children to the bus stop, but waited for almost an hour for the bus to arrive due to new school location. However, they said they plan on keeping their kids in the new building for the entire year.BX public schools open todayP.S. 51 teachers prep for first day of classes