3 weeks is excessive. At my school we have 2 INSET days on the MOnday and Tue, Reception kids are then in for an hour with a parent on the Wednesday, on Thursday and Friday they are doing either a morning or an afternoon, then I thnk that's it, in full time from the following week.
I think this is just about right. You can't compare it with nursery. Most kids who go to day nurseries have been there since they were babies - they will all have started on a random date depending on when their parent's maternity leave ended so induction happens gradually.
Talking of induction, as an adult we mostly get some sort of induction when we start at a new workplace. We are not thrown in and expected to know everything from the second you arrive there and just left to get on with it. (unless you're a supply teacher 😉) We are shown processes and procedures, maybe do some time doing some e-learning elsewhere, taken around to be introduced to people, maybe have meetings with a mentor, go to resolve any IT problems you're experiencing or problems with your security pass etc. It all takes time and allowances are made in terms of how productive you are. Yet somehow parents on here are suggesting that our very small children don't deserve the equivalent for this huge change to their lives? They are expected to just get on with a full school day, with all the new processes and rules and expectations of independence, new faces, etc as if they've always been there? Try to put yourselves in their shoes.
I can't agree with just throwing very young children in all together in a class of 30 on day 1. It's not in their best interests. You also need to consider that times have changed and now mainstream schools have to take children who clearly have often quite severe extra needs, which many parents seem to either be in denial about, or fail to mention on their child's school application and for whom it will take months if not years in some areas to get an EHCP in order to provide funding for one to one support.
All those parents saying that all the children should be in full time from day one, I wonder whether you would have the same opinion if you knew your child was getting hit every day of the first week by a child who is clearly struggling without support. How would you like it if it was YOUR child who was struggling, but not enough attention could be given to them to assess their needs quickly so they coulld get support, because school policy had been changed after parents had demanded a full time education for the whole class from day one?
It's in everyone's interests to ensure that all children can get adequate indvidual attention when they first start school and the staff don't know them at all. Why a parent would want to deny their child that I have absolutely no idea, it's like the empathy gene is missing in some people.