Billy Joel is a proud papa! The 77-year-old has revealed that Della, his eldest daughter with wife Alexis, has graduated from elementary school and will now make the big shift to middle school."Congratulations to our elementary school graduate! We now have a middle schooler," Billy shared with fans on Instagram alongside a carousel of pictures of Della over the years, including with her younger sister, Remy.Billy Joel and wife Alexis with daughter Della"Mommy and Daddy are beyond proud of all your hard work and determination. Your first day of school seemed like yesterday. Amazing things are in store for this girl."Della, 10, will now move into sixth grade, but has already revealed her passion for performing, appearing on stage several times with her papa. In 2018, a then-three-year-old Della joined her dad on stage at Madison Square Garden to sing "Don't Ask Me Why" – her favorite song – while wearing pink Christmas-themed pajamas. Billy Joel's daughters Remy and Della (R)She also appeared with her sister Remy for the last show of his residency at Madison Square Garden on July 25, 2024, picking up a microphone and singing along.The first picture in the carousel showed Billy and his wife Alexis posing with a smiling Della, who held up her graduation certificate, and Billy looked noticeably healthy, a year after he shared he had been diagnosed with NPH, normal pressure hydrocephalus, a brain condition that can affect hearing, vision, and balance, and took a step away from the spotlight as a result.