Louis Sachar was born in East Meadow, New York, in 1954. His family moved to Southern California when he was nine and he attended college at the University of California at Berkeley. During his last year of college, he received school credit for working at Hillside Elementary School, an experience that inspired him to write his first children's book, Sideways Stories from Wayside School. Many of the characters in the book are based on children that Sachar taught and the teacher is based on Sachar himself. Sideways Stories from Wayside School was published during Sachar's first year at Hastings College of Law in San Francisco. He did not know if he would be able to support himself by writing children's books, so he continued his legal education. He graduated from law school in 1980 and, after passing the bar exam, became a lawyer.
Sachar continued to write children's books even as he practiced law. After eight years of writing books and practicing the law part time, he decided to focus solely on his writing. He met his wife, Carla, while visiting the school where she worked. They married in 1985. Carla, a school counselor, served as the inspiration for a character in one of Sachar's most popular books, There's a Boy in the Girls’ Bathroom. In 1987, Sachar and his wife had a daughter named Sherre. Sherre was four years old at the time that Sachar began his popular Marvin Redpost series, and it is for this reason that Marvin has a four-year-old sister.
Sachar does not talk about his work before he finishes a book. He thinks that if he does not allow himself to talk about his books then he will be more motivated to write them down. He generally revises his work four or five times before sending it to the publisher, and after that he often revises it again. In addition to writing children's novels, Sachar enjoys skiing, playing guitar, chess, and cards. Some of his favorite children's authors are Katherine Patterson, Lois Lowry, and Walter Dean Myers.