More expenditure doesn't mean better quality or does it?

I always wonder why public education system in California does not understand that more money spent per pupil in California schools does not necessarily translate to the better quality education. Take a look at the data here (taken from SJUSD school record) The data is for specific school Williams elementary in San Jose. The school district spent about $9,500 per student where as this particular school spent $8,200 per student. Please note that Williams is the top school in the San Jose Unified School district with 2009 API score of 965 (a gain of 16 points). More data can be found on Ed-data website.

There are two more schools in Almaden Valley that comes close as far as API is concerned. So why $800 per month spent on a kid is not making our education system better? The table below shows the percent of students achieving the proficient level and see how kids are doing in all 3 major area of basic education. This is a 3 year comparison chart and the Williams school data is compared against data that belongs to school district and state of California.

While spending less money per student, Williams school is achieving higher score in English, Maths and Science whereas district is lagging far behind. Does this worry you as a taxpayer or a parent? To dig deeper into how taxpayer's money is spent on education, see Dept of education portal.