Saturday, May 7, 2011

NWEA Scores Provide one window on student achievement

I"ve begun a series of posts on how the Board of Education and our educational leadership is using data to monitor our educational progress. One of the ways that we measure student progress is to use the NWEA's nationally normed progress indicators in math and reading.  Information about the NWEA testing system is widely available.  I've posted about the NWEA testing system in the past.  You can find those posts here: (Board gets Accountability Results) and (More About NWEA Accountability). See also:  St. Cloud Board of Education Uses Achievement Data to drive Continuous Improvement

The table below is a cutting from the testing results for this year.  The scores are reported as "RIT Scores."  A RIT score RIT stands for Rasch Unit, which is a unit of measure that uses individual item difficulty values to estimate student achievement.  RIT scores create an equal interval scale.  Equal interval means that the difference between scores is the same regardless of whether a student is at the top, bottom or middle of the RIT scale, and it has the same meaning regardless of grade level.

On this table, you see, for example, that the the national math median score for Kindergarten entering in the fall is 148 (Fall target).  The national median for first graders at the beginning of the year is 164, and the median for the second grade at the beginning of fall is 179.    Another way of looking at this is that from kindergarten to first grade, the median score rises nationally by 16 points, and by 15 points from the beginning of first grade to second grade.  You can find all of the RIT scale norms for NWEA math and reading tests by clicking here.  

 Let's take a look at what we can learn from this data.

The first line tells us that 734 students took the test in kindergarten this year.   The median RIT score for these students, coming into the district for the first time, was 144, or about 4 points lower than the national median.  We've marked the median for our school district in red for KG fall entrants, because the median entry score is lower than the national median.  What does that mean?  

We need to start by recognizing that the median is a measure of the middle score.   It doesn't tell us about the top 25 percent of students, and it doesn't tell us about the bottom 25%.  It merely tells us the cutoff score that divides the top 50% of students from the bottom 50%.   Recognize also that District 742 has a higher rate of students who come to the school district not speaking English, and a higher rate of students with learning disabilities.  So we would expect to find the median entry score somewhat lower than the national average. One of the dangers of looking at the median is that it doesn't tell you very much about how most students are doing.   A school district can have a large number of highly proficient students and still have a lower median. Moreover, the goal in education is not to raise the median score of a group of students.  The goal in education is to assure that all students reach their potential.    We are dealing with children here, not statistics.

What can we say about the magnitude of the difference in median score from the national average? Its about a quarter year behind.   The median score of kindergartners is about 1/4 of a year behind.   Now some students are going to be much farther behind, and other students are going to be quite a bit behind.  

Notice that the standard deviation for entering kindergartners is 11.7.   The Standard Deviation is a measure of how spread out numbers are.  A low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values.  Roughly, we might expect that about 34% of the students score between 144 and 155 when they enter kindergarten and about the same percentage score between 133 and 144.   The children who score below the median may score below for a variety of reasons.  Perhaps their parents haven't read to them.  Perhaps English is not their native language.  Perhaps they are just running a bit behind, as children at this age often do.  Perhaps they have a developmental delay or disability.  Our challenge, as educators, is to help these children grow. Whether they are behind or ahead, they are not statistics, they are god's children.

In winter, this year, the same group of kg students were tested and their median score was one point below the median (for winter).  Because the median score is below the national median, by one point, we've marked the score in red.   That's kind of ridiculous, really, because the one point diifference is almost meaningless.   Its a just a smidgen below.   We could say, also, that the cohort of Kindergartners made up a couple of points on the national average.  Whether that is significant, I leave to you.  Keep in mind, again, that some of the kids may have advanced significantly more, and others significantly less than the median growth.   These statistics are merely one window on what is going on in Kindergarten this year.    Let's not make the mistake of overstating their value.

Let's look at the first grade scores a bit, now.  When politicians and pundits, and sometimes school people, look at statistics like this, they make the mistake of saying that the first grade scores were 17 points higher than the Kindergarten scores.  That's a mistake, because these are two entirely different classes of students.  We can't compare the first grade scores to the kindergarten scores as if the first grade "progressed" or didn't progress beyond the kindergarten, because we aren't measuring the same students.   We see that the median score for first graders this year was three points behind the national median, and that by winter test-taking time, that same class had a median score equal to the national median (for winter).  Similarly, we see that the median score for entering second graders was three points below the median, and then by the winter test, the second grader St. Cloud median was at the national median.

Now we are looking at the aggregated scores, here.   But classroom teachers are looking at individual student scores and they are trying to assist students, all of them, to grow.   They can see whether a student enters behind, and they can see whether the student is catching up, or falling further behind. They can look at NWEA growth scores for demographic subgroups of particular students.   If they try a new teaching technique, or find a mentor for a student, they can see whether that approach seems to be engendering growth  The NWEA growth patterns help us at the Board level to monitor progress in the aggregate.  But the NWEA individual scores help parents and their teachers to focus in on whether the individual student is behind, or ahead the median, and whether they are making progress.

In the next post, I'll look at some further ways that we can use NWEA scores to focus our attention on student growth and student achievement.

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