What is the name of the school principal?

The school principal in Arthur is Mr. Haney.

Mr. Haney is the principal of Lakewood Elementary School, where Arthur Read and many of his friends study. He is known for being absent-minded and good-natured, and the series frequently uses visual comedy involving his unfortunate luck. A recurring gag in early episodes has objects accidentally falling on his head or mishaps occurring around him.

The character's first name is given as Francis Haney in later references, although some Arthur material has used other details or simply called him “the principal.” His secretary is Miss Tingley, who often helps clarify his speeches and school announcements. Mr. Haney also has dyslexia, a trait shared with George, another character in the series.

Mr. Haney eventually leaves Lakewood to build a school in Tanzania, as revealed in the season-20 episode “The Hallway Minotaur.” Miss Tingley temporarily takes over afterward. Mr. Ratburn, by contrast, is Arthur's classroom teacher, not the school's principal.