Not sure if the three year old stayed with you during mat leave but for sure everyone is learning a new hierarchy, etc. It sounds like the two siblings are allowed to rough house at home in the name of "play" and do not know when to stop it.

What about suggesting to the parent that the older child may have outgrown the program and be ready to move to a preschool/daycare centre. That would separate the kids during the day and give each one time to do their own thing. I would imagine the younger one will settle down with some firmness on your part once the older sibling - likely the instigator is gone. Also speak to the parent about the behaviour and how it is not acceptable at daycare and that only if they put a stop to it at home will be able to be stopped at daycare and that if it doesn't then the older child needs to move on away from the younger one.

When we are irritated by our co-workers we don't want to work there anymore and for daycare providers our daycare kids become our co-workers of sorts as we share the same space, resources, facilities and interact. I am finding that I am getting frustrated some days because it seems like we accomplish nothing beyond changing diapers, feeding, napping as in nothing fun. I do miss having the older kids who could follow rules and sing along with me and not look confused when I try to do anything academic.

For sure getting rid of those that irritate us the most does make for much more enjoyable day. I would start there before deciding that it is time to quit totally.