Try a search of the FRS & MURS frequencies.
Did you try a search of the FCC database, they could be there.
Also narrowing down VHF or UHF would help.
And lastly use a scanner with an attenuator at close range. this could take awhile to find the frequencies.
A local high school near me uses three frequencies. one for the staff, one for physical education staff? And the last one hardly gets used sounds like maybe crowd control during events?