You raise a good question. I coach for an organization where it is the policy to call all the young ladies who have tried out, whether they make the team or not. We try to make the calls in timely fashion, absolutely no more than 1 week, most often within 48 hours. As difficult as it is to disappoint parents and players, we think it more ethical and humane to speak directly, rather than leave it up to inference -- as in "if we haven't called you by Tuesday, you haven't made the team." We do this for all age groups 12-U through 18-U.
I wonder what folks think about this question, but also the flipside as well. How long should an organization wait? In my line of work there is an "industry-wide" standard for how long an offer can be on the table. I'm not suggesting that we institute a standard, by the way. I'm just interested in what other teams and organizations do. If you offer a young lady a spot, how long (generally) do you keep it open?