I see several people did not read what I posted above. I know it is long and probably boring to read. I'm not going to retype all of that. If you want to know how I justify what I'm going to say you can read it.I was faced with the same dilemma as you. First time chicken tender, I did a lot of research. I came to the conclusion that if you brood indoors for 6-7 weeks, their immune system is developed enough to send them outside.
If the chicks are exposed to the bug that causes Coccidiosis for two or three weeks they develop an immunity to that strain rf Coccidiosis. If they are not exposed to that bug they do not develop immunity. If they do not get exposed to that bug they do not develop immunity no matter how much medicated feed you feed them. If you raise them in a sterile environment and never let them develop the immunity they need their immune system is not strengthened against Coccidiosis.
I copied this from a veterinarian website. There is no need to gradually withdraw Amprolium. You can eat the eggs from hens fed Amprolium.There is no substitute for a clean, and dry environment when brooding also. If you brood outside, then I would recommend medicated feed. If you feed medicated feed, be sure and have them weaned from it before their first eggs. I've read that the medication will be in the eggs and shouldn't be eaten. Keep corrid on hand.
Amprolium is a common anticoccidial medication used in the treatment and prevention of coccidiosis in chickens and turkeys. In the United States, it is one of the few medications approved by the FDA for use in egg laying hens. There is no withdrawal period.
See more at: https://www.poultrydvm.com/drugs/amprolium