In the case of elementary school, though, you are dealing with kids young enough that they probably cannot reliably be counted on the get ready and leave for school on their own, and so you need to fit school times in with their parent's work schedule.
I know live in a wealthy school district (with very good athletic programs) and high school starts at 9am.
In both places at least some of the athletic/band programs started before school.
Just an anecdote though, I never heard that rationale from an official source.
It's slightly different from no-DST in that "the sun is directly above" is no longer approximately noon, ever; the TZ is effectively 1 hour off of what is should be and DST is abolished. (The sun would be overhead at ~1pm year-round.)
(It would also mean that during winter, in some locales, the sun would not rise until after 9am. I personally like seeing the sun in the morning.)