Bennett, who founded the FSSA in 2001, attends the school's graduation ceremony every year, but because his tour won't allow him to attend the event this year, he decided to call Gaga to surprise students on their last day of school.
The 87-year-old singer and Gaga spoke about jazz, music, creativity and took questions at the school's Tony Bennett Concert Hall in a panel moderated by NBC's Lester Holt. Bennett later performed the classic "The Very Thought of You" followed by Gaga's rendition of "Every Time We Say Goodbye."
The school's choir closed the event with a rendition of Bennett's "Smile" and Gaga's "Applause."
Gaga and Bennett met in 2011 when the two performed at the Robin Hood Foundation benefit gala. The duo reunited later to record a duet of "The Lady Is a Tramp" that was included on Bennett's DUETS II album.