All of the children mentioned are very poor. However, they are all very different as well.
Burris Ewell is particularly dirty, and he only comes to school once a year. We know that his father does not care about him, and never feeds him or clothes him. We also know that he does nothing to help his family and alleviate their poverty. The Cunninghams, on the other hand, are poor, but they are always respectful, educated and clean. They are also very proud. Finally, Chuck Little, while also very poor, is a gentleman and is kind to others. The main reason why the children are so different, despite their similar limitations in financial terms, is because they all had very different levels of parental attention and education.