High School Etiquette

So, I am nearing the end of my first year teaching high school. And wow, the future is in very interesting hands. Two days ago I was with some students at a pull-out assembly that was a musical/dramatic presentation about Cesar Chavez. It was done by a husband and wife team and was very informative as well as entertaining.
Well worth the time out of class.
But, the students... not mine of course- I would've killed them.
They were so rude! Talking during the presentation, not participating, acting 'too cool for school'. I was infuriated! Literally it was all I could do to not stand up and let everyone have a piece of my mind.
People on the phones, listening to music, talking to their friends, putting their feet up on the back of the auditorium chairs. I was so embarrassed to be among that group.
I gave so many death glares to students I don't know. Serious death glares- and they can be scary. Trust me.
I hate the lack of class and etiquette. It is appalling to me. I always feel like even if a performance isn't great you should at least respect the performer for having the guts to put themselves out there. And it's just getting worse.
I also hate the fact that I hear the 'F' word all the time. It's starting to creep into my brain on a regular basis... Yesterday I heard a kid in the hall saying, "I just tore my 'f-ing' pants" I wanted to say to him- just curious but what makes your pants so 'f-ing'? But, I am sure I wouldn't want to hear the answer.
Oh and don't even get me started on the vile things they talk about when they think I am out of ear-shot. It's disgusting.
And very sad- they shouldn't be in such a rush to deal with such adult things. They need to enjoy being young and should stay innocent. But in this environment, that is nearly impossible.
I just wish that respect and tact and refinement would make a come back with these kids. I wish they could learn.
And so I try to set and example, and I try to get through to them.

Maybe I will make a difference?