The education of a child is significantly affected by both the attitude of the parents and the quality of the child's school and teachers. I would not say, however, that the parents' attitude is necessarily the more important of these two factors.
A good parental attitude definitely helps a child's school progress. Studies have shown that Asian students are often higher achievers in school than their American counterparts because Asian parents usually take a more active interest in their children's education. Educationally minded parents can in fact compensate to a certain extent for a poor quality school or teachers. Such parents might provide extra work at home, encourage the child to read more or study by himself or herself. Concerned parents may even hire the services of a tutor.
On the other hand, educationally minded parents arc usually not enough to ensure the good education of a child. Parents often don't have the resources of a good school, or the collective knowledge and training of a good teaching staff. Furthermore, time or money may limit what the well intentioned parent can actually do for the child's education in practical terms.
Consequently, although parental attitude and quality of school and staff are both important to a child's education, I don't feel that one is necessarily more important than the other. Perhaps ironically, it is usually the children of educationally minded parents that end up being sent to good schools with good teachers.