I teach elementary, and Im teaching my kids about the right brain vs the
left brain. I tell them that there is no way that they are doing their
very best work if they're talking because their brain wont let them,
they need to be in their right brain... if they continue talking than I
tell them that I would rather have them sit out so that they dont mess
up their artwork, if they sit out it will be for the rest of the period.
I know this sounds strick but it usually works! some time I get classes
that just feed off each other (like my 3rd graders this year!) and then
I tell them that if they sit out then they get a pink note that goes
home to be signed by a parent and brought back... if it isnt brought
back than they do written work..
hope this helps