-Have a strong voice
-First calmly tell them to settle down and if they dont..
-Shout at the top of yo lungs,"KNOCK IT OFF"
-If they dunt listen,Write down their names and once the teacher comes, report to her.
-Dunt be protective of your friends
-Report to the teacher and ask her to take strict action.
(If yo clasmates only talk then dunt write down their names ,but if they make halla..then you too halla bol!! :P))