I got a question for you: Alan Paul, later a member of The Manhattan Transfer, originated the role on Broadway. It is not uncommon for the role of the Teen Angel to be held as a dual role by one of the other characters in the cast during stage adaptations (in Paul's case, he also appeared as bandleader Johnny Casino). It was recorded by Frankie Avalon (who, like Fabian, was a client of Bob Marcucci's during his heyday) for the 1978 film adaptation of Grease, a role he reprised on stage through the 1990s and early 2000s. The Wild Angels recorded an earlier version for Decca Records in 1972.

Based on this passage, who sang beauty school drop out in grease?
Let's think first:
The relevant information to answer the above question is: It was recorded by Frankie Avalon (who, like Fabian, was a client of Bob Marcucci's during his heyday) for the 1978 film adaptation of Grease, a role he reprised on stage through the 1990s and early 2000s.
Therefore, the answer is Frankie Avalon.