What was just an average day for 99% of middle schoolers around the country quickly became the best day ever for students at Harlem's PS 161. Just as the kids were getting pumped up to Beyonce's 'Move Your Body' as a part of the 'Let's Move' fitness campaign, the 'Bootylicious' superstar came out to showcase her moves alongside them.

The scene was like a real-life version of Beyonce's 'Move Your Body' music video, only in this pop-up version, you can see that the kids were completely surprised by Beyonce's appearance -- and she loved being the one to throw them off.

The music starts, and as usual, the kids get into their choreographed dance routine, but about halfway through the first verse the Grammy-winning R&B songstress bounces in to join them! Surprisingly, the youngsters manage to keep calm and collected for the most part, and even complete the dance with B leading the way.

Did we mention Beyonce is rockin' stilettos as she marches across the (slippery) gym floor? Props to her for that -- and for making these kids' year!

Watch Beyonce Dance to 'Move Your Body' at Harlem's PS 161