SIL says teachers are lazy and selfish for requiring her non-disabled child be potty trained

My SIL has been putting off potty training my nephew. The older one was wearing underwear most of the time by the time he was 2, only wearing diapers to bed. It was hard finding him underwear because he was a little kid and was potty trained quickly. He had to be done with diapers by 3 and a half because I know that he was trained before the younger was born.

The younger is 4 and a half, planning on starting school next year, and they were special ordering him pull ups because the stores didn't carry any that fit him (ironically, he's a pretty big kid. Not fat, he just grew fast). My mom tried telling her that a kid needed to be able to handle his restroom business alone to be allowed in school.

She waited for me to be there and asked me, assuming I'd tell mom she was wrong. But...no. No school is going to change your 5 year old because you were too lazy to do so. The kid knows when to use the bathroom, he just doesn't feel it's needed because he doesn't want to stop what he's doing. He will shit his pants, finish what he's doing, and bring her a pull up and wipes and say "My butt is icky." It's insane.

He usually uses the potty with my mom and I, but at home he was just shitting himself. She then asked if teachers would at least wipe the kid if they wouldn't change him, and I said that's a no. For one, that's not their job, and for two it's too much liability. I told her that while I teach middle school, if I taught prek I wouldn't even help a kid fix their pants. I'm not having someone say I was doing something inappropriate. I'm definitely not walking into a room without cameras and touching a child's butthole.

She said that teachers were being lazy and selfish for this, because she now thinks it's normal for a kid to be nearly 5 and not potty trained. Thankfully potty training has magically accelerated now that she knows it means she'd have to keep him at home for another year if he wasn't totally potty trained come August.

I teach secondary because I don't even like helping kids tie their shoes and blow their noses. I hate that in middle school I regularly have to remind kids to wash their hands after taking a piss. I'm not wiping a kid's ass and I hope none of you elementary people are being forced to do so. (obv if a kid has a disability that makes this necessary that's different. I mean a totally neurotypical kid who'd just rather finish watching his episode of pokemon than use the toilet)