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Teachers don't see that many kids in a year. Breaking them down into a combination of a few demographics is oversimplifying things to such a degree that I real

by jbooth 16y ago

Teachers don't see that many kids in a year. Breaking them down into a combination of a few demographics is oversimplifying things to such a degree that I really don't get how anyone can be so blase about it. I mean, just to start with: * Are our tests measuring the right things? * Are we measuring the right things about the kids? * Are we capturing all of the data for the things we do measure about the kids? Those are huge unanswered questions to just be like "oh yeah just average the results for the income quintile, bang, done, we know who the good teachers are". If a student's being sexually abused at home, and test scores dramatically decline year-over-year, is the teacher a worse teacher for it? Just one edge case. Throw in 4 more and you've got a significant fraction of the scores that the teacher will be evaluated on. These are students' futures and teachers' jobs we're talking about, remember.. I think general teacher resistance to having some sort of oversimplified system shoved on them from above is a feature -- that system needs to be good enough to buy them in before being implemented.

yummyfajitas 16y ago
Lets crunch some simple numbers. Suppose 1 in 100 children is sexually abused for the first time in any given semester [1], and a teacher has 4 classes of 30 students each. Then in 2.5% of classes, a teacher will have 4 sexually abused children (vs an average of 1.2). When this occurs, the percentage of children failing will increase by 2.3%. So lets say on average, a teacher is expected to have a failure rate of 20%. 2.5% of the time (roughly once in their career) they get unlucky and have a failure rate of 22.3% instead of 20%. This will occur 2 semesters in a row about one time in 1500, i.e. it will happen to 1 in 50 teachers (assuming a 30 year teaching career). Alternative numbers, to show that I'm not using cherry picked numbers: P(abuse)=0.001, P(4 abuses in class of 120) = 2.56e-6, slightly greater impact (failure rate goes up to 23.3% over 20%). If sexual abuse happens at a higher rate (e.g. 2%), then we get into the rather implausible situation that 48% of children are sexually abused, resulting in them failing school. [1] I don't know the relative proportions, but this seems like a high number. Among other things, it would imply that at least 24% of children are sexually abused, resulting in them failing school. We are also assuming the child has a good upbringing and good grades until the sexual abuse, which I imagine is not the most common situation. The assumption that it is the first instance of sexual abuse is important, because if it occurred in the prior year, it would likely affect their prior year grades and hence their current predicted grades.
- jbooth 16y ago
  Well, my point wasn't that child abuse happens at whatever frequency, my point is that a whole universe of stuff happens that isn't captured by those statistics. Again, I do think that some sort of unified performance measurement is important. But it's really easy to screw something like that up. Teachers spend between 5-35 hours a week with a student depending on schedule and we're summing up that interaction with information that fits on half of the back of a business card? That doesn't tingle your spider sense at all? "Warning, lots of information loss here"? When you base performance on a metric, then you re-orient everything around the metric. It is very very very important to get that metric right and a right answer probably doesn't fit in an HN post. I mean, nobody thinks engineers should be measured by kloc, let's not oversimplify for teachers either.

by jbooth 16y ago

yummyfajitas 16y ago

Lets crunch some simple numbers. Suppose 1 in 100 children is sexually abused for the first time in any given semester [1], and a teacher has 4 classes of 30 students each. Then in 2.5% of classes, a teacher will have 4 sexually abused children (vs an average of 1.2). When this occurs, the percentage of children failing will increase by 2.3%. So lets say on average, a teacher is expected to have a failure rate of 20%. 2.5% of the time (roughly once in their career) they get unlucky and have a failure rate of 22.3% instead of 20%. This will occur 2 semesters in a row about one time in 1500, i.e. it will happen to 1 in 50 teachers (assuming a 30 year teaching career). Alternative numbers, to show that I'm not using cherry picked numbers: P(abuse)=0.001, P(4 abuses in class of 120) = 2.56e-6, slightly greater impact (failure rate goes up to 23.3% over 20%). If sexual abuse happens at a higher rate (e.g. 2%), then we get into the rather implausible situation that 48% of children are sexually abused, resulting in them failing school. [1] I don't know the relative proportions, but this seems like a high number. Among other things, it would imply that at least 24% of children are sexually abused, resulting in them failing school. We are also assuming the child has a good upbringing and good grades until the sexual abuse, which I imagine is not the most common situation. The assumption that it is the first instance of sexual abuse is important, because if it occurred in the prior year, it would likely affect their prior year grades and hence their current predicted grades.

jbooth 16y ago
Well, my point wasn't that child abuse happens at whatever frequency, my point is that a whole universe of stuff happens that isn't captured by those statistics. Again, I do think that some sort of unified performance measurement is important. But it's really easy to screw something like that up. Teachers spend between 5-35 hours a week with a student depending on schedule and we're summing up that interaction with information that fits on half of the back of a business card? That doesn't tingle your spider sense at all? "Warning, lots of information loss here"? When you base performance on a metric, then you re-orient everything around the metric. It is very very very important to get that metric right and a right answer probably doesn't fit in an HN post. I mean, nobody thinks engineers should be measured by kloc, let's not oversimplify for teachers either.