Re: Frustrated with aikido kids classes
Bail. (That means quit, walk, away, stop trying.) You've talked to your sensei, he sees the problem and won't fix it, and the guy teaching kid's classes doesn't want to be corrected by you, there's nothing you can do in this situation. Don't complain, don't criticize. Just walk away.
Thank your sensei and the kid's teacher for allowing you to be the assistant for that class, but tell them you find you no longer can fit them in to your schedule. Focus your efforts on your own training. Maybe sometime in the future an opportunity will open up to affect the kids' classes, but you can't do it now.
If your sensei asks you for an honest assessment of the kids' classes and won't let you say no, only then should you tell him what you really think. But I doubt he will--it sounds like he's already heard it.