A couple of other ideas....
Unless this is one -huge- high school, needing 2 repeaters is a bit overkill. I'd even go as far as to say needing -any- repeater is probably overkill.
It's easy enough to set up one analog repeater with two separate tones, one for security, one for facilities. Neither group would need to hear the others. But, before you jump on that, consider that situational awareness for -all- the staff can come with some benefits. Simply locking out the janitors because they are not security guys might not be the best idea. A single channel analog solution would be much more cost effective. User training will take care of the rest. Facilities radios can be set up to not allow transmitting if the repeater is already in use by security. You would also likely be able to use the existing radios if you stuck with analog. If you do go with DMR, it's going to require all new equipment.
Also, do NOT(!) pick radio brands, technologies, or any of that before talking to either a consultant or a reputable radio shop. Salesmen just LOVE customers that walk in with a predetermined idea of what they need, especially when its something expensive/new technology/elaborate. They'll be more than happy to sell you exactly what you ask for. They have a 6th sense of knowing exactly what your budget is and figuring out a way to exceed that.
Instead, have a well thought out list of expectations for radio coverage and uses as well as an agreed upon budget. Walking into a meeting with a sales guy not knowing what you want or how much you can afford is going to end in disaster. Realistic expectations are very important. Key word is "realistic". "Radio coverage everywhere" is not realistic. P25, full AES encryption, AVL/GPS/Man Down/IP67/Intrinsically safe/ etc. are not realistic. No matter what, someone will find a place that even the most expensive radio system will not cover. Usually something like 95-97% coverage is considered pretty good. Getting from 97% to 99% coverage will often double the price. Getting 100% coverage is going to bankrupt you. Even the best built public safety systems won't have 100% coverage.
If you do go with a repeater, a well placed system running a few watts would be plenty. 50 or 100 watts to cover a high school is a red flag, and will probably be rejected by the frequency coordinator.
Consider having the district (if this is a public school system) look at a district wide system. Since these systems can be expensive, it can make a lot of sense to look at the bigger picture, not just a single campus. That may also get you better funding.
One item you should consider is that at some point someone is going to forget radio protocols and transmit student information overt the radio for everyone in receiving range to hear. It would be wise to consider some form of simple encryption on the security or administration channels/talk groups.
Keep in mind that a repeater will need to be licensed. That will likely require frequency coordination, so make sure you figure in the costs of that, having someone knowledgeable do the applications and an experienced shop set up, program, install the repeater.
Before spending money on a repeater, you -really- need to look at the overall costs. You are easily looking at a few thousand dollars to do this correctly and legally. There are other solutions...
Cell phones. I know, security guys don't like cell phones, they want two way radios, but someone in control of the money is going to ask this. There are cellular "radios" that actually look like two way radios, but work on the cellular network. Bonus is you'll get incredible coverage.
WiFi. Likely your school already has some level of WiFi coverage. It may be considerably cheaper to add a few WiFi access points in strategic locations to cover the entire campus. Plus, you likely already have (or nearly have) pretty good in-building coverage. There are some good WiFi radios on the market. Icom has a pretty good system. Benefit is you can easily expand coverage by adding WiFi access points, and often that funding will come (at least partially) from the IT side. Other benefit is depending on how the networks are set up, you could expand coverage to other campuses relatively easily.
I'd still say get someone to look at your existing radios and make sure they are up to snuff. 4 watt UHF should do pretty well. I wouldn't rule out issues with radios.
