About to fucking blow up on a teacher tomorrow! Update

My step son is 6 and in kindergarten. After school his daycare picks him up in a van and then me or my husband pick him up at 5 depending on our work schedule. I picked him up from daycare and he had a jacket around his waist and smelled really strong of urine. I asked they daycare about it and they said he was like that when they picked him up. I asked my step son if he had an accident at school. He told me he asked the teacher if he could go potty but she said no. He asked again and she said no and then he had an accident. All the school did was give him a jacket to put around his waist. They didn't give him new pants or even call me, my husband, or my son's bio mom to bring him son. They just let him sit in pee! My friend has had issues with that teacher not letting her daughter go to the bathroom and I'm gonna go blow tomorrow. These are kindergarteners! How can a teacher be so cruel to tell a 6 year old they can't go potty! And then let him sit in pee!

Update: The teacher told me the reason she didn't let my son go to the bathroom is because he was in time out for crying... I'm not even kidding. He got upset he spilled his drink and started crying. She said she's been trying to teach him not cry over small stuff.... Seriously... And when I asked why they didn't give him new clothes or call anyone of us to bring him pants she didn't have an answer and didn't say anything. I blew up on her and the principal. The principal apologized and promised they would be more sympathic to my child's needs from now on. I'm still pretty pissed though.