Due to the fact that Walter has to work for his daddy, education is likely not stressed at home. On the other hand, Walter does appear to go to school every day that Scout is there. How hard can 1st grade be? Was there really homework? Couldn't he have at least learned some things while he was there?
If you ever get the chance to study Maslow's hierarchy of needs, you will find that our needs works from the very basic of survival (air, food, water) all the way up to something called self-actualization. This is where we quest for who we really want to be.
Walter's basic needs aren't met. Until that is achieved, he has no chance to even make education a priority.
In the book To Kill a Mockingbird the Cunninghams are very poor people. Walter attends school without shoes and with feet that look permanently dirty. He has been walking through the hog pens and ground without shoes all summer. Walter's family is so poor that the boy never has lunch to bring to school. His parents refuse to take any type of charity.
Walter's father has been one of Atticus' clients who had no money to pay. Mr. Cunningham works hard to find ways to pay Atticus by bringing him walnuts and turnip greens, chopped wood, and holly.
On page 24 Walter is eating lunch with Scout after Jem invited him and he tells Mr. Finch that he can't pass first grade because he has to stay out of school every spring. He tells Atticus that he has to help his dad with the crops and the chopping.
"I've had to stay out ever' spring an' help Papa with the chopin', "
Walter has to work for his dad and education is not that important at home. Walter does go to school but even his basic needs aren't met and he does not wear shoes so it would be pretty hard to focus on education when he has a lot to worry about.