The city’s Department of Education is standing by Greta Hawkins, the principal of PS 90, who recently decided to switch up the musical portion of her kindergarten class’s moving-up ceremony. They were set to sing “Proud to be an American” —a real crowd-pleaser and tear-jerker at this mostly immigrant school — but Hawkins was wary of “offend[ing] other cultures.” (Several years ago, Hawkins tried, unsuccessfully, to do away with the daily Pledge of Allegiance and “America the Beautiful” regimen.) The Department of Education also offered an alternate explanation to the New York Post, one that none of the school’s staff had heard: Hawkins believed the lyrics “too grown-up” for the 5-year-olds. So she went with something appropriate for all ages: Justin Bieber’s “Baby.”