Re: Age differences in class
Up until his recent retirement, the oldest student in our dojo was 83. The man stood about 6', was whipcord thin and very strong in his grip, and I don't mean just for his age. He's probably the only student in the dojo I've never heard complain of soreness or injury. I could tell you some stories, but I don't think you'd believe 'em.^^
Nevertheless, age does take a toll. While he could still take ukemi, we couldn't throw him or take him down at full speed. This is, of course, an extreme example, but it illustrates the basic principle.
In our dojo, we teach our students to time the speed of their throws to the speed of the attack. The basic rule is, the stronger your attack, the harder you are thrown. Our students pretty much abide by this rule, and when they don't, they are corrected instantly. This rule is irrespective of age. We've had young students who were not yet up to taking fast ukemi, and older students who preferred it (mostly because, once you know how to do it, fast ukemi is easier on the body).
So teaching students to abide by this rule is one way of keeping the kids from trying to act out on their seniors.