Bumping this question because I think it got lost
(the question was about breeding from pullets) Now I am pretty new to breeding to the SOP and what not but here's my observation and from reading a LOT. Oldtimers recommended breeding from no less than hens going into their second laying year. Because their eggs are usually bigger than during their first year, but also because you should have a record of their production from the first year (this generally presumed you were trapnesting or at least keeping records by each pen of birds)
Also because at that age you will have weeded out a lot of birds over that time, those that were just not thrifty, if any got sick or egg bound or whatever....
That said I know a lot of people hatch from pullets, especially when just starting off with a breed; you want to get chicks on the ground soon as you can. I'll be hatching from pullets this spring because you never know what is going to happen to a bird. And I want more of them as quick as I can. Next year when I have hens and pullets I might wait and hatch from the pullets later.
I am waiting for the pullet eggs to get to a reasonable size tho, so the chicks aren't too small at hatch. I know they will probably catch up in a couple weeks to hen size chicks but haven't ever done a side by side comparison