There is a quick and easy answer to this question, since everyone should get an education as soon as possible, but as you know from reading the book, there is no way that Ruth would have been able to get a college education when she graduated from high school.
The situation was not one conducive to going to college for a number of reasons. First, this was the middle of the Depression and getting a college education was not as much a priority as food, shelter, and clothing. Ruth's family was not the poorest, but life was a struggle for them. Another difficulty for Ruth was her sex. Had there been any money to spare for college, that money would go to educate a male, since women were expected to marry. Finally, Ruth had been staying with her New York relatives during her high school years because of her pregnancy, and when she graduated, she felt a strong need to escape from her family for a number of reasons. Going to college would have meant help from her nuclear family or help from her New York relatives, and she needed to be able to take care of herself by earning a living.
Getting an education was not as much of an option for Ruth. Ruth was raised in an abusive situation and the first chance she had to get out, she took it. Once she moved to the big city she got wrapped up in having some freedom and enjoying life. Ruth also had to support herself and getting an education while working was not as much of an option when Ruth was young as it is for women now a days.
Ruth married and started having children. She put her children and her faith in God first. Her sacrifices were so that her children would have an education. Of course having an education would have been nice for Ruth, but her life was not the same as lives today. Because she dated black men, she was already a social outcast and I am willing to say that some colleges may not have allowed her to attend based on her marriage to a black man.