Research has shown that the ability to learn something new (like Greek grammar) depends on the ability to accommodate the new subject matter to what you already know. When my beginning Greek grammar in college told me that the Greek noun system works just the Latin noun system, that analogy might have been helpful for students who already knew Latin grammar, but not for students (like me) who didn't.
I had come to Biola with no prior background in the study of foreign languages. That's mainly why I dropped out of my beginning Greek class after only three weeks. When a student "gets" what's being taught in a classroom, it's a lot like someone "getting" a joke. Something clicks in the brain. Students with the requisite background knowledge will get the joke, but students who lack that background will be puzzled until someone explains the background of the joke to them.
Even really smart students don't always get the joke. (I'm not saying I'm smart!)
The dilemma that Greek teachers often find ourselves in is this: If we tap the breaks too often while the lagging students acquire the background information they should have gotten in earlier grades, the progress of the entire class is bound to be excruciatingly slow for the better-prepared students. If, on the other hand, the teacher plows ahead (like my teacher in college did) instead of slowing down for the laggards, the less-prepared students inevitability are left further and further behind. Either way, continued momentum for all is demonstrably false. The required skills and/or background knowledge for such readiness is very unequally provided in the student's background and environment. I myself attended a public high school in Hawaii that lacked a foreign language requirement. Additionally, I was a lazy student and preferred surfing to studying.
Ideally, students enter a beginning Greek course should share enough common reference points to be able to learn steadily. It's arguable that this rarely if ever happens. Hence what I try to do in my classes is roll the ball down the middle and hit as many pins as I can. I accept the fact that some students are better prepared than others for the curriculum. This means taking the time to tutor students who are falling behind. As long as they keep up with their memory work, I am happy to do so. At the same time, I give extra credit (in the form of extra work on all quizzes and exams) to those students blessed enough to have gained the needed background knowledge at home or at school. My goal is that BOTH groups will gather momentum as the semester proceeds and that ALL of my students will progress steadily in their studies!