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Misconception: TVAAS should always indicate growth if the percentage of students scoring Proficient or above increased since last year.

Comparing the percentage of students who score Proficient (or above) over time does not account for changes in achievement within performance level categories. Comparing the proficiency rate at a district or school over time does not account for changes in the cohort of students included in the rate. TVAAS value-added reporting follows the progress of individual students (as a part of a group of students) over time, regardless of their achievement level, to ensure that all students count.

TVAAS in Theory

Imagine the scenario below. The ELA achievement level of Student 1 is represented by the line with the blue diamonds, and that of Student 2 is represented by the line with the red squares. The orange and purple lines show the percentile corresponding to the Approaching and On Track performance levels. The achievement level of Student 1 has steadily increased over time while the achievement level of Student 2 has steadily decreased over time. From seventh to eighth grade, Student 1 moved from the Approaching to On Track performance category. From seventh to eighth grade, Student 2 maintained his position in the On Track performance category although his achievement level has gone down.

STUDENT TESTING HISTORY IN TCAP ELA FOR STUDENT 1 AND STUDENT 2

By considering the number of students who have scored On Track and assuming all other students have maintained the same performance categories, the number of students has increased with the addition of Student 1. However, this does not consider that Student 2's achievement level is steadily decreasing over time. A subtler approach is required that considers the growth of all students regardless of their achievement level.

TVAAS in Practice

TVAAS does not measure students' growth based on the number or percentage of students who tested On Track or Mastered, as compared to previous years. TVAAS detects these subtle changes in progress even within performance levels. As a result, educators are recognized when they make growth with students outside the "bubble."

Furthermore, it is important to remember that the proficiency rate and growth rate are two different metrics, each designed to show a different perspective on students' academic experiences. Proficiency rates provide a snapshot of students' knowledge at a specific point in time whereas TVAAS provides a measure of students' change in achievement over time. The district/school proficiency rate might increase or decrease from one year to the next due to changes in the student population associated with the district/school rather than an increase or decrease in students' growth. For example, some students might transfer in and out of the district/school. In fact, an entire grade of students will enter the district/school calculation (such as third graders) while an entire grade of students will leave the district/school calculation (such as eighth graders). As a result, changes in proficiency over time might not align to changes in growth over time. TVAAS cannot measure the growth of systems and schools with high mobility rates.

TVAAS value-added analyses provide reliable and valid estimates of the effectiveness of systems and schools, including those with high mobility. This is because TVAAS can include students even if they have missing test data, so that the growth of systems and schools is representative of the students served.