I Thought that you fed the chick-starter until 8-9 weeks, then either grower or flock-raiser until they start laying. When they start laying, you can either switch them to layer feed, or leave them on flock-raiser and supplement with oyster shell.
I think part of the confusion comes from the names given to the feed. Around here it's hard to find "chick starter". Chick starter/grower is readily available. Mine were on that until they reached 19 weeks and I got my first egg, then I switched them to layer.