I have one of those "sassy" students. Speaks loudly and needs to be the
center of attention. He will never change. However, he does respond to
polite, consistent sternness. I have given detention, sent him out of the
class and sent him to the Dean. When he acts up I have to respond quickly.
You do need to pick your battles. When the whole class is talking and
working, but his voice stands out - is it disrupting to others, or just you?
When I need everyone's attention I have to be stern with him. It works. Plus
I have to remind him (and many other students) constantly to focus on work.
These students are a lot of work. You must stay on top of the situation.
Hope this helps a bit. Martha