We are a school, with two C25 controllers (I'll call them A and  serving about 45 3705i APs, deployed about one per 2 or 3 classrooms. All classrooms get decent signal strength (-50 to 60 dBm or higher), usually from multiple APs -- but we are increasing the AP density in some areas in order to reduce load per AP during periods of high client density such as online testing sessions.
We recently added two APs in one area already served by two other APs on controller A. The newly added APs joined themselves to controller B. All APs have exactly the same VLAN and SSID config, and most clients had usable signal strength from at least three APs. We did NOT try to set all the APs up as a load-sharing group.
The first time we had a high client load in this area (about 25 devices per AP), we noticed that over 90% of the clients were getting on the original APs with only a few on each of the new APs. All APs show the same signal strength (max 13 dBm).
Any idea why only a tiny fraction of the clients are connecting to the new APs?
Another question: The group of APs is not literally "line-of-sight" since they are in different rooms separated by sheetrock-on-metal-stud walls, but they do overlap. Should we configure them as a load-sharing group, even if it means moving either the original or the new APs from one controller to another to get all of them on the same controller?
Thank you in advance for any advice!
