I have found that if a see begginers being neglected I just up the tempo of the class considerable for the higher grades, dont give them a break when they are training with each other.
They soon work out the only way to get a rest is to slow down the tempo themselves and train with the lower grades.
I have not really come across people who cant shut up. maybe it is sign that the class is boring them?
people not doing the technique demonstrated bugs me actually. For a student to do technique not in the way that is demonstrated is very arrogant, basicly saying that they know better than the instructor.
Our instructor had a talk to us about this not too long ago, pointing out that there are so many ways to do technique, one day he may do it one way, the next another... each instructor will do it differently also. Trying the different ways gives you options and adaptability and so there is probably a reason why he did it one way and not another.
So, you follow the class plan and do as he is doing.
the tidying up the mats is annoying sometimes too.. especially when you get to the showers and the lazy people who didnt tidy up have run off all the hot water!