I don't actually know what the usual method might be. DS was so far out there that the school just saw him coming in preschool and they gave him the WJIII to see where he was and document it for having him skip kindergarten.

It wasn't until DD was in first grade that we first heard them say they usually don't do any identifying for gifted until third grade! They just have the sense to recognize the real outliers before that. DD isn't one of those, so she's just on normal track so far.