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Misconception: If students are already high (or low) achieving, it is harder to show growth.

Educators serving high- or low-achieving students are often concerned that their students' entering achievement level makes it more difficult for them to show growth. However, with TVAAS, educators are neither advantaged nor disadvantaged by the type of students that they serve. The modeling reflects the philosophy that all students deserve to make appropriate academic growth each year; as such, TVAAS provides reliable and valid measures of growth for students regardless of their achievement level.

TVAAS in Theory

The value-added models used in Tennessee are designed to follow the progress of individual students over time and estimate whether these students made the average amount of growth observed in the state in the current year for the subject (for EOC) or subject/grade (for TCAP) of interest.

Furthermore, although TCAP and the EOCs are designed to discriminate proficiency from non-proficiency, they are also designed to have sufficient stretch to measure student performance at a wide range of achievement levels. Accordingly, there is sufficient stretch in the TCAP, EOC, and Grade 2 assessment testing scales to measure the growth of high- or low-achieving students.

In fact, any test that is used in TVAAS analyses must meet three criteria, and the TCAP, EOC and Grade 2 assessments meet these criteria. The tests:

  • Must be designed to assess the academic standards.
  • Must be reliable.
  • Must demonstrate sufficient stretch at the extremes.

Some educators are concerned about their students who make perfect scores and how that might impact their value-added reporting. In truth, very few students make perfect scores in the same subject from year to year. In 2019, the number of students who made a perfect score in consecutive years for TCAP Mathemathics was a tiny fraction of a percent—only 0.0211%. In the other TCAP subjects, it was even less, ranging from 0.0005% in Social Studies to 0.0014% in Reading.

Some educators are concerned about their students who make very low scores and how that might impact their value-added reporting. TVAAS is focused on growth rather than achievement, and this approach uses multiple years of data, when available, to follow the progress of individual students over time. The growth model itself assesses whether, on average, the achievement for a group of students increased, decreased, or stayed about the same over a period of time. This can happen regardless of whether students' prior achievement was relatively low, middle, or high. In other words, educators are not disadvantaged by serving low-achieving students who are not yet proficient.

TVAAS in Practice

Actual data might be the most readily apparent way to demonstrate that high- or low-achieving students show similar growth as other achievement groups. The figure below plots the average achievement for each school in Tennessee against its growth index (the value-added estimate divided by its standard error) for TCAP Mathematics in grades 4-8 in 2019. There is typically little or no correlation between the school's academic achievement and the growth index. In other words, the dots representing each school do not trend up or down as achievement increases; the cluster of dots is fairly even across the achievement spectrum.

TENNESSEE GROWTH INDEX VERSUS AVERAGE ACHIEVEMENT BY SCHOOL