Hello,
We are deploying Chromebooks at our school as well. When we had our initial deployment of devices, I had 25 chromebooks in a room with one IAP-105. I can't tell you exactly why, but it performed horribly. The chromebooks were losing their connections left and right. I finally unplugged the AP and went with a different vendor for the day. The other vendors had very slow connections, but at least they did not drop the connection all together.
I am now ordering an IAP-135, hoping that the additional antennas and streams will help out with the density of devices. For anyone wondering, the IAP-105 was the only access point running at the time, and it was located hanging from the ceiling in the center of the room.
My takeaway from testing Chromebooks is that they are very, very bandwidth needy, expecially at startup.
If anyone has had a different experience with Chromebooks (Samsung XE303), I'd love to hear it! I really want Aruba to work!
Good luck!