Clear goals help, thoughtful pegagogy is important, the right environment makes soul-transformation possible, but I've found that the right person (as part of the right team) doing the teaching is the only make-or-break.
(written at Camp Ramah New England, where I'm watching
a small army of the "right people" in the "right environment"
with a powerfully clear mission prepare to change the souls
of over 800 children this summer.)