Gwinnett’s elementary and high schools were down on an important statewide performance index, but slightly up for middle schools, according to data released Monday.

Gwinnett School of Mathematics, Science and Technology was the top-performing high school in the county for the 2012-13 school year, based on information from the Georgia Department of Education.

Osborne Middle School ranked first among middle schools in Gwinnett while Partee Elementary was the county’s top-performing elementary school, the data showed.

Schools and districts are receiving grades through the state’s College and Career-Ready Performance Index, which uses student test scores, academic progress and closing the gap in performance between groups of students to come up with a numerical grade of zero to 110.

To get a look at all the results for schools in Gwinnett and across metro Atlanta, check out MyAJC.com.

Georgia’s elementary and middle schools performed better in 2012-2013 than they did the year before, according to the data. High school performance was down slightly.

Among districts in the heart of metro Atlanta, Atlanta Public Schools got higher grades on the elementary, middle and high school level. Cobb was up on the elementary and middle school level and down on the high school level. DeKalb was down on all three levels. Fulton was up on all three levels.

State officials expect the grades to become a key indicator of how schools and districts are performing. Some, however, have questioned whether any single grade could adequately capture the performance of schools and districts. Others complain that the grades rely too heavily on standardized test scores and don’t give enough credit for improving student performance.

Grades from the 2012-2013 school year were supposed to be released in November, but department officials pushed that date back as they changed the way the grades are calculated. Now, more emphasis is given to academic progress.

Search our interactive database at MyAJC.com to see how your school scored and keep checking back for additional updates.