What is One Year Growth?
In simple terms, one year of growth is the amount of growth a student makes during a school year. Fastbridge assessments represent growth using the rate of improvement (ROI) metric. Depending on the assessment, the ROI will measure the change in score over weeks or months. For example, the ROI for aReading represents the average monthly growth between two administrations. Therefore, if a student scores 472 on aReading screening in August and 495 on the same assessment 9 months later, in May, then that student will have a growth rate of 2.56 scaled score points per month.
When considering the question, what is one year of growth in an educational setting, what is often of interest is the answer to the question, what is typical growth among the population of students? That is, how much growth should I expect students to attain in one year?
This is a normative question that often anticipates a single value at or above which a student made one year of growth, and below which a student did not make one year of growth. Such an approach neglects the variability in growth across the student population and the imprecision of test scores that will naturally vary from day to day. Furthermore, it neglects the instability of growth due to other factors that vary throughout a year and across students such as the quality of instruction, social-emotional states, life events, and brain development as well as the phenomenon of regression to the mean. As a result of such factors students who make lower-than-average growth during one interval, often make higher-than-average growth in the next. The amount of growth one should expect to see from students will differ.
One Year’s Growth “Expected Annual Growth” From a Normative Perspective
Unlike proficiency standards derived from expert analysis of what students should know and be able to do, to date there is no external criterion to define growth standards. Rather, growth standards are typically norm-referenced. That is, characterizations of growth are anchored on the distribution of growth scores in a national sample.
Fastbridge provides ROI growth norms that can be used to describe typical student growth rates within the student population. The ROI growth percentiles indicate how a student’s growth compares to the population of students at each grade and for each assessment. FastBridge provides seasonal and annual growth percentiles: Fall to Winter, Winter to Spring, and Fall to Spring.
The table below presents the growth norms for grade 2 students on CBMreading. For every 5th percentile, the table shows the corresponding average weekly change. For example, a student with a Fall to Spring ROI of 1.55 points per week, grew at a rate at or above 70% of the students in the norm group.
Statistically speaking, what is typical or expected growth is commonly understood as that part of a score range where most students fall. ROI distributions are generally normal, bell-shaped curves. In a normal curve, the most common score is the mid-point or median. On the percentile metric, the median is the 50th percentile. Half of the population has a slower growth rate while the other half has a faster growth rate. As such, the 50th percentile is the most reasonable approximation of one year’s growth. Thus, the 50th percentile is a reasonable standard for establishing growth expectations.
Limitations of Using a Single Cut-Score
All scores are affected by random factors. The standard error of measurement (SEM) indexes the magnitude of the random factors (random error) on a student’s score. A student’s true score at a given point in time is best understood within a range of plus or minus one SEM. For CBMreading, the SEM is about 9 points. Thus, on a given administration, we can have confidence that the student’s true ability score lies within a range from 9 points below to 9 points above the observed score.
Growth scores are also affected by random error. As such a student’s true growth score is also best approximated by a range of values. By estimating the reliability of the ROI scores, we can approximate the range within which a student’s true ROI is likely to fall. On CBMreading in grade 2, a student’s true Fall to Spring ROI is likely to fall within a range of approximately plus or minus 0.30 ROIs. Using the grade 2 CBMreading ROI norms, for a student with an observed Fall to Spring ROI of 1.27 (50th percentile), the true ROI falls within a range from about 0.97 to about 1.62. This is roughly the range from the 30th to 75th national percentile.
Because scores contain random error and given that 50 percent of students fall within the range from the 25th through 75th national percentile, it would be appropriate to treat any ROI within that range as approximating one year’s growth (see the table below).
Student Growth in FastBridge
Student growth information is available in the Group Growth Report and via the Data Download.
The Group Growth Report can be accessed by selecting the Reporting tab and choosing View Report on the Group Growth Report icon (see Figure 1 below) and selecting the assessment to create a report. Once accessed, select Fall as the Start and Spring as the End intervals at the top of the page (see Figure 2). To obtain the ROI growth percentile, the other options at the top of the report can be left as the defaults.
To see the national ROI percentile, select the + icon on the right side of the screen (see Figure 3). The growth percentiles for each student are displayed in the Growth %ile column of the table. The Growth Score column presents the ROI value.
Growth data are also summarized in the bar graphs in the top center window. The categories are defined by percentile ranges and are the same percentile ranges used to define benchmarks or norm ranges in the Group Screening Report. The key at the bottom of the page provides the percentile ranges for the normative view color coding scheme. Although there is not a range that breaks at the 50th percentile, these categories can be helpful to quickly summarize the level of growth in a group.
Users can also download raw data on students to investigate student growth patterns through their own means. Data Download can be selected through the District Manager or Reporting tabs. Data Download is located at the top of the District Manager tab (see Figure 4). On the Reporting tab, find Student Data Download and choose View Report. On the next page, select the school year, schools, and assessment. Select submit and a .csv file will download in the window. The Growth Percentile from Fall to Spring column, found in the data file, provides the national growth percentile of each student based on growth from Fall to Spring.