I shifted a group of 10-11 week olds to pellets this Monday. They're a 20% grower pellet. The pellets are smaller than a layer pellet, and the nutrition is balanced for chicks rather than pullets/hens.
They were a little testy about it for the first day, and very wasteful scattering them on Tuesday. Yesterday they were a bit better about it.
Interesting thing though....we also have some 6-7 week olds. I tried the pellets on them just to see their reaction. They ate them up better than the older chicks! So yesterday, I filled their feeder with only pellets. They gobbled them right up throughout the day with no waste.