The answer might come from how the schools themselves serve those communities. If they have classes taught in Spanish, then by extension, they'd probably expect some radio programming in that language. Think of it from their point of view. It's not necessarily the way a typical radio station is programmed. It's also why at one time some non-com educational stations used block programming rather than format programming.
And by doing that, they fall victim to the same thinking that took KPFK in Los Angeles from low ratings to almost no ratings: they mixed languages and, thus, listener bases. The regular listeners only had to tune in a couple of times and hear programming they did not understand to lessen their usage of the station.
If you buy Sprots Illustrated and find the contents of The Economist, you won't buy that one again.
But try explaining that to a school board.