In the 1978 film Grease, Danny and Sandy attend Rydell High School.
Rydell High is the fictional school at the center of Grease, where Danny Zuko, Sandy Olsson, the T-Birds, and the Pink Ladies navigate romance, friendships, reputation, and teenage social life. The story begins during the 1958–59 school year, after Danny and Sandy fall in love during summer vacation and unexpectedly reunite when Sandy enrolls at Rydell.
The school’s name was reportedly inspired by real American high schools and by popular culture, including the fictional Rydell High references associated with the work of novelist and screenwriter Ed McBain. Rydell is not a real school in the film’s setting, although the production used several California locations to represent its campus and interiors.
Rydell High is easy to confuse with other fictional television and movie schools. Ridgemont High belongs to Fast Times at Ridgemont High, while Bayside High is associated with Saved by the Bell. Grease’s school is Rydell, making that the single canonical answer.