spacing for the upper VHF band

How is this determined?
On 155.205 MHz in my area, there's the Edmonds school district, King County which sounds like medical disbatch, and Bainbridge Island school district. How were all these entities allowed the same frequency so close to one another? To cover roughly the same distance only 2 lp fm stations are allowed on the same frequency.

This is somewhat comparing apples to oranges, but most if it has to do with the two-way services using lower power levels with narrower bandwidth. Also, most two-way communication these days is encoded so that the equipment used for one licensee's service will reject weak signals from the others that don't have the correct "signature".

LPFMs are wide bandwidth (same as full-power FM, obviously) and there is no discrimination by receivers between signals. That's why they have to protect each other and adjacent channel full-powers ... to prevent receivers from finding too many competing signals within a specific range of channels.

That makes perfect sense in theory, but in practice I've heard where it can go wrong, both on a scanner and on the actual recievers themselves. For example, dirt and dust can build up on the mic connections causing the thing not to connect properly. When that happened, we'd hear Bainbridge Island pretty well. On my SDR, I pick up King County pretty well , sometimes even overpowering the Edmonds school district which is what I'm interested in.