Today was the first day I had to use my "Dad Voice." The classroom was getting a bit too chatty while I was trying to carry on my lesson. After a soft-spoken, "Guys?", I barked out a "HEY!" It worked remarkably well. For those of you who don't know me, I'm 51 years old, bald with a gray goatee and, I'm told, broad shoulders. Also, my natural facial expression tends toward the unhappy. Even when I smile, the corners of my mouth turn down.
In essence, I look like way more of a badass than I'll ever be. The look has served me well over the years and kept me out of many a fight. Being able to add both the "Dad Voice" and "Dad Glare" to my repertoire has helped instill general classroom compliance
I imagine this can be a bit harder for some of the younger TAs -- those who are barely 4 or 5 years older than their students, but this is one of those times in life when being old really does have its advantages.
Last semester, while still an undergrad, I had a chance to talk with one of the other grad student/teachers. I admitted to him my nervousness over teaching. He told me not to worry -- They would take one look at me and know who was in charge.
It's a little like spiders; they're more afraid of you than you are of them.
But, I guess like spiders, if you don't crush them, they can come back to bite you on the ass later.