*While First Lady Michelle Obama was busy surprising a DC school with her “Let’s Move Flash Workout,” students at a New York City public school working out to the program’s song from Beyonce got a big surprise when the singer herself walked in and joined them.

About 85 students at P.S. 161 in Harlem were in the middle of a choreographed routine Tuesday to the song adapted from Beyonce’s hit “Get Me Bodied” when the singer arrived. [Scroll down to watch.]

The children were participating in a national simulcast of “Let’s Move Flash Workout,” part of Michelle Obama’s fitness campaign.

The singer joined in wearing stiletto heels and a T-shirt emblazoned with “Let’s Move.”

Thirteen-year-old Aisha Collier gushed “she’s so beautiful.” She told the New York Post she messed up a little when Beyonce first arrived but then got back into it and continued to dance and have fun.