It's a general filtering mechanism. Almost nobody wants to get up at 5 AM to get to school or to the jobsite. If that's what you have to do to get in, this sele

It's a general filtering mechanism. Almost nobody wants to get up at 5 AM to get to school or to the jobsite. If that's what you have to do to get in, this selects for those participants who are more highly motivated to participate in the institution, and differentially rejects those who either lack sufficient motivation to comply, or lack the self-control necessary to execute compliance. A fixed and mandatory early start time serves as a proxy for general discipline and a means to conclusively demonstrate one's willingness to follow instructions and do things in the institutionally mandated way despite personal dislike of them.