You realise, but most don't. The kids whose tests are marked and sent home with the wrong grades, the spelling lists that are sent home for kids to learn with spelling mistakes, the certificates that are proudly borne home by excited children with spelling errors.... Not all teachers, TAs or schools recognise mistakes.
Unless parents are happy to accept that their child is learning errors by rote, or having correct maths answers marked as wrong becasue TAs do not understand the content, then schools are going to have to listen when their errors are pointed out.
Whilst I find it marginally entertaining when the kids come home with a new spelling list with errors on it, I do email the school and let them know. It's no wonder that educational standards are sliding if parents are not able to correct mistakes that teachers make.
My kids are usually the brats that correct the teachers work. So far it has been met with equanimity. They do it nicely. In a polite and mannerly way. The teachers always report it with a mild hint of irony. We are all human.
As a volunteer, I would tread carefully. I would be aware that my role was not supposed to include correcting the teacher's work, but tbh, I think a subtle, away from the kids, friendly conversation about the errors would be in order, whether it jeopardised my future volunteering or not. If the teacher doesn't know they are imparting shite, all the more dangerous for the kids who are not at the point where they are able to question it, themselves. Think of it as safeguarding their learning, and possibly helping the teacher to do a better job.
Yes, I have taught. Yes I have been in classes as both a TA (well, LA for SEn kids) and volunteered. I know my place in whatever role I happen to be in, but standing by and letting schools teach rubbish to children they have a duty to educate isn't a role I will take.