Gosh I'd have to say I would think most 3 y/o could be expected to pick up their toys. ODD started Montessori daycare at 18 months and all the toddlers knew they had to put away the 'job' they were playing with before they could get another one. She figured it out the first day there by watching the other kids and brought the behavior home after a couple of months as well. I'm not the greatest enforcer but at 3.5 she usually picks up when I remind her, and often enough when I don't.
Getting my 3 1/2 year old to obey..need some consequence ideas! - Page 2
We have one child who finds tidying extremely difficult and one who has been able to do it from a very young age. It's getting slowly easier for the eldest.
We picked up with them, singing songs, counting, ordering them into colours or size or furthest away etc - in other words it's a game and it's learning time. Now I still break it down for the eldest and that still helps him.
I didn't punish for not doing it. But I'd give rewards that I tried to make relevant to the tidiness - like 'now the room is tidy we can pull out the train set together' or now it's more like 'if the room is tidy early we can watch that film' or 'once it's done you can have your computer time'. Also, a consequence of it not being tidy might be, 'well, we can't get any more toys out because there's no room for them so we can't play in here any more.'
Doing as they're told - being too rough in their play or not realising other kids' boundaries is a great example of something they need to learn how to do rather than not do if that makes sense - learning what to do instead of carrying on hugging when the other child is saying no will help. I didn't punish for that. Yes, I'd remove a child who wouldn't step away on their own, but saying, 'gentle touching - like this' helped, as did talking and reading about feelings - their own and others'. What is it like to feel cross with someone else? How do you feel when someone is cross with you? I feel like this etc.
I agree with an earlier post - this is the long game. It takes longer than making them do/not do things because there will be a negative consequence otherwise, but it seems to be helping them understand and make choices in a range of situations that I haven't specifically helped them with before and I think their confidence and feelings of self worth are appropriate partly as a result of this 'helping them learn' approach over 'making them do it' through negative consequences.
I hope that makes sense. The book How to talk so kids will listen and listen so kids will talk set it all out for me.