Couple Questions:
1. When you say connect to an AP, do you mean you are connecting to an active wireless network and the IP you're getting from the wireless network is from the DHCP server at the High School?
2. I assume MS = Middle School, but please clarify.
If #1 above is true - i.e. you are connecting to the wireless network and obtaining an IP from the DHCP server at the HS, then this means that all APs are tunneling traffic back to the main controller and the VLAN associated with the wireless network is from the HS, which is using the HS's DHCP server. Since you have 1 controller and APs at 3 locations, you can do one of 2 things:
1. Setup split tunneling but there may be some negatives that you would have to look at the admin guide to compare split tunnel vs. tunnel mode.
2. If your DHCP scope for this specific network is running out of IPs, then create additional VLANs for the wireless network in question and use VLAN Pooling.
The above assumes a few things about your design but if you have additional questions, post some additional info about your network setup.
I would also highly recommend taking a look at the VRDs for design ideas that would be helpful to your environment.
-Mike