As soon as you start talking about the bell curve, you show you do not have a lot of understanding of educational theory. Unfortunately, that is true of many people in the field of education. It was taught for a long time, which is why so many people still think of it as a valid concept.As to the second point, the bell curve is the bell curve. You will always have students that will fail (or should have been failed), simple statistics will tell you that.
In theory (and only in theory), the bell curve reflects the abilities of the general population. That is what, again only in theory, you would see in the classroom when a class begins. It should never reflect the results of the class after those students have encountered a well-designed curriculum and the efforts of a skilled instructor to help those students who need more assistance to reach standards. If the actual results of a fair assessment at the end of a class end up in a bell-shaped curve, it is a sure indication of really bad instruction.
But most assessments that show a bell curve are not the results of fair assessment. In my early education classes, I was taught how to manipulate assessment design to create a bell-shaped curve of results. That is what happens with tests like the SAT--those tests are manipulated continually to make sure the results fit a bell curve, with 500 as the median score. It was not until much later in my career that I saw the research that showed that a fair assessment of student learning in a well-taught class will never, ever produce anything like a bell-shaped curve.
To start with, few, if any, class populations contain the full range of natural abilities. The higher the level of the class, the more the bottom range disappears. That was in part my point about screening--in a self-selecting scuba class, the people who do not have the ability to succeed are simply not there, or at least they would not be there if the student population were properly screened to keep out those who do not have the prerequisite skills needed for success. Thus, the bottom end of that theoretical bell curve, the ones who you expect might fail, is missing.
The most insidious part of bell-curve thinking is the feeling that it must be applied to a given population, no matter the content of that population of the actual results of assessment. This means student achievement is applied as a comparison of one student to another rather than to a standard of performance. Here are two true stories that will illustrate what I mean.
- My early bell curve teaching went away after a colleague expressed her frustration. She and another member of her department agreed to use the same final exam for a unit they were teaching. They also agreed to apply the bell curve for final grades. (She had a motive--she knew her colleague was absolutely incompetent, and she wanted those results to show that.) When it was done, the very worst score for any student she had taught was higher than the very best score for her colleague's students. But the colleague insisted that the bell curve be applied to each class separately rather than to the combined classes, which is what she had expected. As a result, his class scoring range was the same as hers, even though his best students had not done as well as his worst. She had to fail students who had done better than students who got A's in the other class.
- A student at Brown University, an elite Ivy-League school where all students are top of the line, went in to his chemistry teacher for mandatory grade counseling near the end of the semester. the purpose of the counseling was to allow students to know where they stood going into the final exam. The school had a policy that allowed freshmen to drop the class without penalty at that point. The teacher told him that he had an A average going into the final exam. She asked him about his life goals, and he said he wanted to be a doctor. She said she thought he would be a good one. He got an A on the final exam, and was shocked when his final grade was a B. The teacher explained that when the students who were failing the course dropped out, it shifted the curve, dropping him to the B range on the bell curve. In fact, she said, if one fewer student had dropped out, he would have stayed in the A range. He said something about his dream of being a doctor, and the teacher said, "Sorry, but you will never get into med school with a B in freshman chemistry."