Just anecdotal experience, but my experience as childminder and as parent is that children have their own rate of progression, and while the 'graphs' in their red book and then at school are a great tool in many ways, in my case, I constantly worried DC1 (son) was behind the curve...
I knew in my head, 'it didn't matter, they progress at own rate', but I was still quite angst-ridden :o)
So DS (now Y3) was always a little 'behind' academically and socially, slight concern from his reception teacher...and then all of sudden, half way through Y1, it was like all pieces slotted into place, and he took off. In every which way, and nothing to do with me, just the right time I think! He's now much more sociable (though never life and soul of party), and predicted level 5 for the end of the year in numeracy and literacy (not smug- honest, just to demonstrate how he's blossomed by himself, in his own time, at his own pace).
DD (Y1) talked and walked early, keen as mustard for wanting to sit and draw/ write name/ do jigsaws, super start in Reception, and doing well, but much more of a steady progression on the curve, and probably at same stage DS was in Y1.
So think I am saying what Indigo did - they all progress at different rates, and as long as they get appropriate support at home, they'll get there.