Why do San Mateo schools have such mixed academic ratings?

My children are reaching elementary school age, entering Kindergarden in the next two years. I have begun researching our local elementary schools and to my dismay, our local school, Laurel Elementary is a 6 out of 10 (greatschools.org). There is only one public school in San Mateo that has a 10 out of 10 rating, while the others fall as low as 2 out of 10!! How can there be such a vast difference between the best and the worst school in the same district, with little evidence of anyone doing anything about it?!

As I was discussing with neighbors the other day about the difficulty of getting into Baywood through an inter-district transfer, I started wondering why the district can not work on getting more rigorous about their curriculum and verifying the effectiveness of faculty on a regular basis. There are many tried and true ways in which the school can improve their academic performance; and it seems this could be remedied in an area full of actively engaged, concerned parents.

In such a high value area of California, a highly rated public school should not only exist in the "North of 92" area.