Well, those disrespectful, immature students could have been me 20 years ago! [blush. I'm ashamed to say
] Different people take different amounts of time to realise their flaws and how to behave! The younger me was also pretty insecure and hyperactive, both of which drove my ridiculous behaviour!
Try and see their vulnerable side! And don't assume they'll drop out etc.... 20 years later and I'm now the lecturer. I was often drunk/stoned/asleep when I should have been at seminars! But somehow I scraped through those days, got a 2.1 (phew!) and eventually found my path!!
I do get pretty annoyed sometimes when I see those students like I used to be! But I try and remind myself that my job is to engage them, not judge them, and try and be that one person that can inspire them and change their direction to one which could serve them well in the future (rather than one which entails more booze and more hangovers).
A good lecturer can inspire even the most distractable student! If your students are talking, or not turning up, or walking out, you need to do something different!
There is nothing more rewarding than the drunk, 3rd/failing student who turns it around because you, or a colleague, actually inspired them to make a change :)