Is yelling discipline?

Today being like every other day, Trent and I set off to school. Seeing only his cherub like cheeks through the hat and big coat, made me want to cover him in kisses...but we were running late!
In the car we discussed how he is going to have fun at school and that Daddy will be picking him up. All is well, until we get to school. We proceed to the classroom after minutes of peeling layers of clothing off. And we see that both PreK classes are combined for "Sister No Name" to do their weekly singing. (Trent goes to a private/catholic school) This "Sr. No Name" was my teacher when I was in grammer school and I know how she scared the crap out of me then! Well, Trent is a good boy and sits in the circle, throws me a kiss, I catch it and the door gets closed. Well I began to have a conversation with the PreK teacher about the upcoming Valentines Day party when we hear a child crying. I knew instantly that it was not mine...like a mother lion, I could identify his cry anywhere! But none the less, it was a child crying. Well, not a second goes by and Sister No Name screams..."STOP CRYING...STOP CRYING THIS INSTANT!!!!!" The room feel silent..then she starts singing again. Does this beast understand that she is dealing with 3 and 4 year old little children who just started to trust the outside world? Well, here comes the mother lion again! I turn to the teacher and say..."listen, I don't' like that, it is not appropriate and I think she needs to be re-evaluated about her teaching skills" The teacher agreed but she is 25 years old and new...what is she going to do...stand up to a nun that has been in the school for 125 years? No..it is up to me to protect these children. Old school does not work, I think that a student should have respect, and a lot of it but to have the child fear a teacher is not going to benefit them at all. Is yelling discipline? Maybe it worked then but I know that it only makes my child nervous...these kids are smart...you could raise your voice but to scream? No way!
So me, Mrs. Lion is meeting with the principal today and I am going to voice my concern over her behavior. I am hoping her tenure does not impact the need for a discussion. We shall see...I will pump Trent for information...he is very vocal...and very honest! Gotta love it!