January 1956
Principal Strickland's office
It's been two months since that event at the dance. Match, Skinhead, and 3-D have constantly made fun of him since he was scared of George McFly and the other students. He has lost interest in school in general so his grades have been quickly declining endangering him from graduation. He is actually a super senior due to his poor behavior and grades. This would be the day Biff would decide to drop out of school and start doing things for himself.
Strickland: Biff Howard Tannen! Your grades have been declining the week after the dance! You have been skipping classes/school, skipping detentions, have not been completing assignments, never completed any exams, and constantly showed up late for school! You will be a super duper senior next year!
Biff: You know what, I don't need this dumb school anymore! I have decided to drop out! (runs out and slams the door)
Strickland: Whatever you say Tannen! Don't screw up on your future!
At his house…
Gertrude: Biff! Biff! What are you doing home early!
Biff: Didn't Principal Strickland call you! I have decided to drop out of school and start my own life!
Gertrude: What?! Why?!
Biff: My grades have been declining due to my lack of interest and I won't be a super duper senior next year!
Gertrude: Then buzz off you young bastard!
Biff: I'm about to! So goodbye ya old hag!
Gertrude: Whatever Biff! Get out now! Dealing with you the same way I dealt with your father being expelled from school for destruction of property!
Biff: Your and grandpas fault he ended up that way! (goes to his room and packs his bags) Later grams!
Gertrude: Later ya chicken! (Biff slams the door and leaves the house with his car)
After dropping out, Biff worked at the local car shop as a mechanic and in the 60's would start his own auto detailing business. His business doesn't become popular until the 70's. His auto detailing business was viewed as good but many of the citizens received complaints on Biff cheating them out of a second wax of coats. Gertrude dies of natural causes in 1961. He met the love of his wife Anne the same way they met in the original timeline, at a party. They married and had Tiff in 1968 and Biff Jr. in 1973. Anne left in 1977 and divorced him in 1980. She left Tiff and Biff Jr. with Biff Sr. because she didn't want to have the responsibility of taking care of her kids alone.