So it's True!

Today was a great day, I got work done, had a great lesson, and avoided the principal all day!
There was one major "event" that bothered me.
I came to school early like I usually do, and found one of my class' morning teachers sitting there. Now she's usually there at this time, and that's when we catch up on news, and talk about our students.
Today she was beside herself with something that had happened in her class.
Her brother had gotten married last week, and because of it, she was behind with some of her sheets she gave out to the class. Today, she had given out more stencils than she usually did in an effort to catch up to where she should be. She gave the class the stencils to be filled out for homework, and although there was some grumbling and a general attitude of unhappiness, these stencils were for homework and that's that.
Well, one student came over to her after the class, and started talking to her in such a disrespectful, fresh way, that she was shocked.
This girl never uttered a peep in her class, and now she was saying things the teacher never expected to hear from anyone, least of all this quiet kid!
The student called her an idiot, and said that she was mean and crazy..and she did it all to the teacher's face! She even shook a fist at her.
The teacher told me she had gone to the principal, shocked, and the principal begged her not to say anything to anyone. This student comes form a very important, respected family, and she didn't want the word to get out. She told me that the girl's mother was called down to school, and something was going to be figured out.
The teacher didn't tell me the girl's name, but I guessed, and I got it right.
The teacher was shocked, and asked me if I had ever seen her act this way. I told her the same thing she told me, that she was the quietest girl in the class. I knew, because she was the one who gave me the index card saying that she went to an anger management class every Monday after school.
The other teacher was shocked! I was too, to tell you the truth. It's true that she had told me about her problem, but I had never seen it, so I kind of put it out of my mind, almost believing that it was a made-up story trying to get my attention.
Wow.
The bottom line was, we agreed to keep it between us, the other teachers never ad a problem with her so we didn't feel they had to know, and we figured that if the mother was being spoken to by the principal, the mother herself would probably tell the school about her problem.
What I can't figure out is, why does a situation have to reach this point before a parent will tell the school some important information that we should've known 100 years ago!?!?
I said it as a teen, and I'll say it as an adult.....I'll never understand parents!!