If you look here, there are lots of commercial stations below 100MHz, although I have noticed that NPR tends towards the bottom of the dial.
I said “effectively”, which on reread doesn’t convey the meaning I wanted it to. I meant that given the option, the FCC tends to put commercial stations above 100 MHz and non-commercial ones below, but in some markets that simple division is not possible.
IIRC, some rural areas do have two radio stations at one frequency. Well, it’s one radio station, but during football games, people from one area tune into the left, and people from another area turn their balance to the right. Both games can then be broadcast.
Actually it’s the part of the FM band from 88.1-91.9 Mhz that’s reserved for non-commercial stations. That includes NPR and college stations, religious and community-non-profit stations.
Technically, a non-commercial station can be anywhere on the band, but the frequencies are so valuable that the commercial stations have generally bought out the non-commercial stations on other frequencies. That’s why the FCC originally reserved a chunk of the spectrum specifically for non-commercials.
That’s what I meant by “educational band”. But after religeous organizations gobbled up all the available station assignments in the late '80s, the term is rather out of date.