District 89 schools improving

Only seven of ten fail to meet standards, an improvement from nine of ten failing last year. See the Pioneer Press.

Can any of Proviso Probe's erudite readers explain how the standards work?

AYP is the minimum level of improvement that school districts and schools must achieve each year as determined under the NCLB Act.

This sentence suggests that schools meet standards based on improvement from year to year. Does this mean that individual students are improving? Or does it mean this year's second graders are scoring better than last year's?