"Are there performance differences associated with WPA2 Personal vs Enterprise?"
For actual traffic encryption i believe they use the same encryption algorithm based on AES, so there would be no difference. The main difference is during authentication. During roaming there may be more over head to join the next AP when using Enterprise, but this should not really be noticable ot the end user unless you have high latency between you network and AAA servers.
Authing devices via MAC is not very secure, and if you have teksavvy students it's only a matter of time before they figure out how to clone a MAC and get teacher access.
What are you using to authenticate your users? If you have AD in the back end you should be able to pass back role information and assign Teacher vs Students to different roles, even while keeping them on the same VLAN in the Aruba infrastructure. if you need to apply FW polices up steam, you might be forced to use VLAN, but i would still suggest role mapping over MAC filtering.
Let me know if you have questions about these options.
_ELiasz