S.E.
Others may not agrees, but if the talking isn't working he needs to have a reason to stop. Time away from the things he enjoys just might be the next step.
I realize others don't agree and that's fine.
We have expectations and we help our children meet them. They make choices, no matter what we've taught, instilled, explained, etc. Ultimately, they make the choice.
If my daughter wants to play after school. She needs to have her work finished. If work is sent home from school because she doesn't do it at school, it is done before any play. Again, a choice she has made has a consequence.
The teacher can work with you on this at school. Together, the three of you should sit down to discuss the situation. Together you can create a behavior chart that rewards him for his positive behaviors in class. Start out with a check mark every 15 or 30 mins. Put him in charge of the sheet and getting the mark (at the end of the period if he can wait that long). The sheet comes home every day. If there are missing check marks, talk about them. Figure out what happened. The rewards happen at home. Eventually move the sheet every other day, every week, etc.
We worked with my daughter's 1st gr. teacher and the sheet worked great. We gave marbles for every check mark. Marbles turned in points that were spent...sleepover =10, 15 min TV=30, etc. She loved spending her marbles. In fact, she saved up her marbles to have a sleepover b-day party. She worked hard to earn enough marbles to invite all the her friends. By the time the party happened, the behaviors were in check and have continued to be in check in 2nd gr. She's no longer making funny commentary that throws off the lesson.
Stephanie