As Egghead Jr said banding is only as good as your other records. I use very few bands anymore. Only potential breeders of pureblood are banded. Average birds are eaters. So "weigh in days" are key to my rooster management in the flocks. My first banding was of chicks. I was selecting for rapid feathering. Now days, the four best purebred males of a breed are banded @ 10 weeks. Each gets one blue band. Then four more blues get put on top perfomers at 14 weeks. At this point I may have six birds with blue bands. I have yet to have more than 6, but the double blue banded birds at this point are visibly superior stock. The first cull takes place at 14 weeks and the worst performing males and any birth defects go. They make decent fryers cleaned up. At day 150 I select my future breeder from the blue banded. Conformation to standard is selection priority. If conformation is about equal then overall size. If size is also equal then width of hips. If width of hips is also equal then length of keel bone. If keel bone length is also equal I must be doing my job at breeding for uniformity.LOL
The pullets are banded similarly with emphasis on laying traits. The first six purebreds of a breed in lay get banded with a red. The first pullet in lay gets a blue too. The date is recorded. The first ten pullets to cease laying get banded white. The last six to cease laying get a red. A double red gets reds removed and a blue instead. If I have a red banded pullet that would end up with a white band the red comes off instead of a white and a blue goes on. Molting can occur in only a few day window of the entire flock as molting is a multiple factor occurance. Vent inspection is used to confirm lay ceasation. At molt the pullets are evaluated. I choose molt because fluffy hens are just fluff. Conformation to standard is selection priority. Barring major faults any blue bands become potential breeders(1 blue) and the best conformation birds get a blue too until i have ten potential breeders. All white bands(short laying cycle), unpersonable and undersized pullets are culled after body condition and feather regrowth is such that they make for an easily pluck.
The breeder flock has a limited roster so only the best of the best get to breed pure. The potential breeder pullets are cross bred and re-evaluated as hens (24 months) with emphasis placed on their overall size, personallity, broodiness, hatch rates, chick rearing, chick vigor, and of course laying record. Each breeder flock is small. Only 4 purebred hens of each breed. Each gets a red and white band to go with the blue. Only then are they "breeders". Those that don't make the breeder cut are culled at this point. A hen with a single blue can always be replaced by an up and coming pullet. The best birds are "made hens" lol 2 blues. These get to live out their days. They are used as breeder stock but not counted as part of the breeder flock. My oldest made hens will be six in June. Fatty the Buff Orp and Oreo the SLW. Both still lay and brood a clutch each June. Superior animals in every way.
Culling this heavily may sound counter productive at first and in the beginning it can be but, if one is dedicated to producing a better bird and a better flock it is absolutely nessessary to cull sub-performance and poor conformation from the flock.
Breed the best eat the rest. And keep good records.