Here's a thought, rather than setup a radio station for pupils. Turn ithe project into an educational task and let them do it.
Plenty of scope for involvement. Starters
IT/Computing refurbish a PC, networking, programming, web design.
Media posters, magazine web design, artwork, literature.
Music composing music for jingles
Business studies, funding the station
Get the idea?
Need help with the studio itself, ask here.
Creating a school radio station certainly used to fit really nicely into PSHE sessions - improving your local environment?
(Guess what I did as my project back in secondary school!)
You could try synergyschoolradio, their packages start at under £5000 and you won't need to renew your license, or support contract. Their software updates are also free of charge. Could be worth a look.