Based on SchoolMatch's standard, schools in Duval County are considered effective when their students perform equal to or better than 80 percent of the students in the match district.

SchoolMatch evaluates student achievement in the match district, and defines the caliber of performance that exists among the top 20 percent of the students there.

This level of performance becomes the benchmark for Duval County schools.

Here's how SchoolMatch developed demographic comparisons for the Duval County school system:

Duval County is unusual because it is larger than most school districts.

It is also poorer than other large districts. According to SchoolMatch, Duval County families don't earn as much money, and the school system doesn't spend as much per student.

So SchoolMatch instructed its computer to find other demographically similar districts.

Similar but smaller districts were added together to create a comparison district that is demographically similar to Duval County.

Then Duval County and its comparison district, or match, were broken down into socioeconomic groups:

The lowest group included schools with students from families whose incomes are under $20,000. It also included schools where more than 75 percent of students are receiving free or reduced lunches.

The highest group included schools with students from families whose incomes are greater than $60,000 and schools where fewer than 15 percent of students are receiving lunch aid.

Comparisons were then drawn between Duval County and its match and between similar groups within the districts.

For example, Sandalwood and Mandarin high schools have students with similar demographic characteristics and were placed in the same Duval County group. They were compared with students in a similar demographic group in the match district.