every kids different and it'll come out when they get curious enough to want to know. My oldest said she knew for a while but didn't want santa to stop comming so she insisited she still believed, I think even now at 26 she would tell me she still believes,lol...dd7 figured it out because she never believed there was a tooth fairy, so if there's no tooth fairy there's no santa, she keeps it up for dd6 who still does. Best wishes...