Son's teacher uses collective punishment. Do I let her be and teach my kid "that's life", or stand up for them?

My 8yo (2nd grade) has come home three times this week in an incredibly bad mood, and when I ask him what's wrong, he tells me he's mad because his teacher keeps canceling free time for the whole class because just a couple students aren't following rules. (This is free time for playing in the classroom, not recess)I feel mad and sad for him, having to pay the price for the behavior of others, but at the same time, I guess it is an opportunity to teach him something. I tell him I know it sucks having to pay the price for things others do, but sometimes that's life. I'm also trying to teach him not to let things ruin the rest of his day.I'm just not sure if I should contact the teacher and find out if this is true, but if it is true, what should I do? Do I try to stand up for my son and the classmates who didn't do anything (why not just send the bad kids to the principal?), or just let her do her thing and stick to my job as a parent and just teach my son that that's life? via /r/Parenting http://bit.ly/2Ivynxo