Rebounds also suffer from so-called "diminishing returns"—the idea that players on the same team effectively compete with one another for boards. Often a particular player—say, Minnesota Timberwolves center Kevin Love—serves as his team's designated glass-cleaner, and he scoops up balls that his teammates might well have grabbed anyway.
The [plus-minus] technique can also examine the impact of top rebounders: Kevin Love consistently rebounds in double digits, but his contribution to his team's total boards is only about two to three per game, according to one analysis.
On the other hand, Love is under 6'8" in his bare feet and is a white guy who can't jump all that great: he doesn't block shots (only 0.4 per game, which is really low for somebody with so many rebounds).
(By the way, my impression is that rebounding correlates better with being a good all-around basketball player than does shot-blocking. The all-time bjg men like Russell, Chamberlain, Kareem, and Walton tended to be great at both rebounding and shot-blocking, but lots of guys are only good at one or the other. In general, the guys who are only good at shot-blocking are more often the weird Manute Bol-type talents. For example, on the playground, I was a pretty good shot blocker but I was an all-time awful rebounder. Partly it was getting pushed around by less skinny guys, but much of my rebounding deficit was cognitive: I never had the slightest clue where the ball was going to bounce. In contrast, I had a pretty good idea when somebody was going to shoot, so shot-blocking strikes me as pretty obvious while rebounding seems like a Dark Art. Your mileage may vary.)
Moreover, despite his superb hand-eye coordination, Love doesn't create much offensively down low (making only 48.3% of two pointers). His team, the Minnesota Timberwolves, has a very bad won-loss record, 15-50, and gives up a lot of points.
For example, say the Freshman coach is great and routinely goes 9-0. All you can do as Sophomore coach is match his record or do worse, which might be an analogy for this New York teacher.
Similarly, the search for a super-sophisticated single number ranking system for teachers can overlook the advantages of less ambitious statistics at pointing out particular strengths and weaknesses, which would be of use both to teacher looking to improve and to administrators looking to maximize the usefulness of a teacher's talents.