If Mary held school and education to be so important for herself, why did she not make sure that her children felt the same way?

Because she was, little by little, losing the motivations of her life and becoming a completely different person.

Explanation:

Although you have not presented the text to which this story refers, we can see, from the context of the question, that you are referring to "Other Wes Moore" that quotes the story of two young people, who even having very difficult lives, in environments completely decadent, they had very different lives.

Mary is the mother of one of the Wes. In her youth she was very studious and valued this in her life, but the economic and social difficulties caused her to lose her scholarship, become pregnant, be abandoned and live in an environment full of violence, poverty and alcoholism. The circumstances in which Mary lived has made her disillusioned with everything that could be good in her life, she becomes a different and completely unmotivated person and that is why she does not care about the education of her children.

- the mistakes that have been done in the past will repeat themselves

- you will trust all the wrong people

i think she wanted to protect her children from the extreme racism of the american south.