Stage3 special needs register

You're very lucky you've got onto the ladder from nursery age. From my experience ( I work in a school) if the wheels are in motion from before nursery or just at the beginning of nursery then they've a better chance of things being in place come September for Primary one. If not September usually February.
After that there's no educational psychologist assessments done again until primary 3 for progression into P4 most times P5.

There's 3 main times for assessments and statements being done. Nursery year for things to be in place for P1, Primary 4 for things to be in place for P5 and then again Primary 7 to get things in place for secondary school.

Anything out if those age years is at the insistence of the parents and backed by the school, and 9 times out of 10 those children have left mainstream school and went to a special needs school.

And even though some children are statemented doesn't automatically mean that a child will get a 1-1 assistant. There are 9 children in our school at present who are statemented but no assistant has been given, they do get some outside support though.