He is your substitute teacher since your normal Teacher is on Maternity leave she had to leave so she could help her husband the baby room color so she picked this one teacher and his name is Bill. He looks at the class and says

"Good morning girls and boys.. I'm your substitute teacher for Mrs. Skyler since she is on Maternity leave for a couple of Weeks. And I would want to interduce myself. My name is Mr. bill or if you want you can just call me Bill whatever works for you girls and boys"