I let my student leaders set the policy about 20 years ago. To receive a letter jacket in our progarm they must qualify for TSSEC and receive a 3 or higher at TSSEC on a solo or ensemble. They may also receive a letter jacket if they make the All State Band. If they do not earn a jacket before their SR year, then we award SR's a jacket. 90% of our students earn their jacket before they are SR's.
I do have a few that choose to wait and get their jacket from athletics.