In baseball, there's an entirely useless statistic called Runs Batted In (RBI). When I was a kid, we would often hear about the RBI leaders and I immediately noticed two trends in RBI leaders. 1. They nearly all played for teams with a really good offense. 2. They nearly all hit at the 4th or 5th spot in the line-up. I was a nerdy little kid who didn't know anything but I knew this was a bogus statistic. See, RBI measures how many runners a batter knocks in. Sounds important, right? Definitely something worth measuring. But it turns out that it's highly skewed. Not every batter is in the position to knock in a run. If you are the lead-off hitter (batting #1 in the line-up) you often bat with no runners on. Also, if you're on a crappy team, you run into the same challenge. So it turns out that RBI count doesn't really tell you how well someone hits for power. For that, you need a stat called slugging percentage. If you want to see how consistent a batter is, go with on-base percentage. If you're looking for balance, go with OPS (on-based plus slugging percentage). In pitching the equivalent is a win-loss record or an ERA compared to WHIP. Total wins is a metric based on a team's overall performance. But the things is, our world is full of seriously flawed statistics. BMI is useless compared to measuring one's actual vitals. Plus, BMI has a really negative history connected to eugenics. Go look it up. It's disgusting. And even today, it's often weaponized against perfectly healthy people when they don't fit the stereotype of "average" that doesn't actually exist. I run 5 days a week. I eat healthy food. My body fat percentage is low to moderate but based on BMI I'm obese. I share all of this because the same thing exists in education. When we use standardized test scores to measure a student's learning (or worse, still, a teacher's effectiveness) we're often running into the same trap as the RBI. We're measuring privilege and positionality while ignoring the data that actually matters. We're running into the BMI trap and failing to embrace neurodiversity. And, like BMI, there's a dark side of psychometric history rooted in eugenics. I'm not opposed to data. I love data. But my love for data is precisely why I hate bad data. My love for data is precisely why I am so opposed to nearly every policy that uses standardized tests to measure learning.