I don't know why so many people on here claim their pullets lay at such a young age. I have raised probably 60-80 hens from newly hatched chicks, I have had the following breeds: RIR, Production Red, Sex Links, Leghorns, EEs, BOs, BRs, Silkies, Ameraucanas, Games, OEGB, and probably some more that I am forgetting.
The SOONEST I ever had ANY of them lay was a White Leghorn who laid her first egg at 22 weeks of age. The rest starting about 23-30 weeks old, and one (Leghorn) didn't even lay until 9 months. The Ameraucanas didn't start until after they were a year old. All the others average about 30 weeks.
I have 5 Gold SLs that are 19 weeks and 2 days old today. They don't look like they are ready to lay anytime soon. I have a game pullet that is 23 weeks old and hasn't started either.
My flock is very, very healthy and they are fed layer crumbles, fresh fruits and veggies, and free range often. I have also hatched out every month of the year, I know seasons make a difference, but I would love to find a breed that lays before 6 months of age. I have yet to find it.