"In this knowledge-based economy, would success be measured by how long students sit at their desk rather than what they learn? I hope not. In an age of customization, would we settle for a one-size-fits-all model that moves kids from grade to grade based on their age rather than their skill level? Hell no. Last year, I said our education system was an 8-track tape in an I-Pod world."
Jeb. Please. Try to understand this.
We don't measure students' success by how long they sit at desks. When they reach certain points in the course (called "End of the Chapter" or the "End of a Topic"), we measure their knowledge using something called a "test" or a "project". Their test or project earns a number called "a grade." We use this number because it's a convenient way for teacher, student, parent and school to communicate how well the student understands "the material". We don't throw away the rest of the information, but we do have the summary number (the "grade").
Over the years, I and many other teachers have taught math. We have learned that students, despite the claim of uniqueness that permeates the socio-political consciousness, are amazingly similar in what they can learn about our subject. (This is called "experience" and it is the reason why "experienced teachers" get paid more.) We know that some students are "good in math" and will cover eight major topics and that others will struggle to learn six. That's why we have different levels of classes - not because we are discriminating against anyone, but because we are intelligent enough to choose the right level for each type of student.
Surprisingly, these different courses COULD be used to "differentiate" the teaching for students, but non-teachers don't understand that each little snowflake is not, in fact, unique. They also don't understand that putting kids into courses that are appropriate for them is the best way for them to learn. Until they think about it, most folks don't see that putting kids into sections in which they are significantly the fastest or slowest learner is LESS effective than separating them by ability. Politicians don't really think and lawyers are paid to refuse to. That's why "tracking" is no longer used.
One other thing. Social promotion is necessary sometimes. When you insist that kids stay back, you occasionally get a non-academic kid (who else?) who is not the best influence on impressionable people. Do you really want that 17 year-old in with your 13yo daughter?