Some of my students are quite disruptive: talk over me and other students, avoid doing tasks during class, etc. They are seventeen and eighteen years old at an in- house apprenticeship program.

Some of my students are quite disruptive: talk over me and other students, avoid doing tasks during class, etc. They are seventeen and eighteen years old apprentices at an in- house apprenticeship program so I am not sure whether some approaches may be too child-like. I have tried setting tight time frames during class and costant reminding of keeping a low tone during class. I have also clearly laid down the rules (be on time, listen to the teacher and to your classmates, do your homework...) but they definitely challenge them. The next step is a written warning, according to the school rules, but it seems a bit harsh. Are there ways/ techniques to get them to follow the rules withouth resorting to harsh measures?