Mark Roulo & Steve H on open vs closed loops

An open loop control system is one in which you don't bother checking to see how you are doing. An example would be a robot arm, where to move to a certain position, one just moves a motor a certain number of revolutions, but doesn't check to see if maybe the gears are slipping.

Open loop systems tend to be simpler and cheaper than closed loop systems, but less reliable.

A closed loop system would be the robot arm with a sensor that fed back the arm position. In this case, even with slightly slipping gears you can get the arm to the correct location because the robot might issue one extra revolution command to make up for the slipping gears.

Poor schools and classrooms tend to run open-loop ... no one knows if the kids are learning what they are supposed to learn. Well run schools and classrooms run closed-loop by checking the kids for progress AND THEN TAKING ACTION (e.g. reteaching). Even better would be a school or classroom that was closed loop on the teaching itself. For example, if kids kept not learning, trying to figure out what to change so that the kids learned the first time around.

I don't get the impression that the second version is done formally in very many schools (or businesses for that matter).

Positive feedback means you do more as you get closer to what you want. I don't think any engineers design these things on purpose, but sometimes you get one anyway (I think ram-jets have a built in positive feedback ... without external controls, the faster they go the faster they want to go until they burn themselves up).

Mark Roulo

Steve H:

"I don't get the impression that the second version is done formally in very many schools.."

Because of NCLB, our state mandates that this process takes place. They send out (almost worthless) questionnaires to parents and students and they hold parent-teacher meetings to review the standardized test results.

For example, the committee might see that the standardized test scores for problem solving in math have gone down a few points. They will sit around and discuss the problem. It's down only a slight bit, so there is not much of a problem, right? Perhaps it's due to the small sample size (they get to sound rigorous). Well, in any case, the administration will tell the teachers in their next meeting to emphasize problem solving more. OK, next problem.

The flaw, as you can see, is that this is all relative. You can provide all of the feedback you want, but if the basic structure of the system is wrong, it will never be fixed. Standardized tests will never tell you that many more kids should be getting to algebra in 8th grade. In fact, it tells the school and many parents the opposite. (They conveniently ignore international tests.)

This reminds me of my son's Science Olympiad project. He can tweak things all he wants, but his basic vehicle design will never reach the required maximum distance.

In our district, "Extra Help" is the answer to all learning difficulties, across the board. Students are supposed to "be proactive and seek extra help." If a student does not seek Extra Help then he deserves his C or D or F. At the high school, students are to seek extra help and also practice "self-advocacy," which means parents are not to contact the teacher or the administration about a problem until the student has tried and failed to solve the problem on his or her own.

This philosophy has now been imported into the 4-5 school. When parents raise an issue with a teacher, the parent is told that the student should have come to the teacher with the problem. It appears that ten year olds are supposed to monitor their learning, seek Extra Help, and self-advocate.