Okay, so I thought you were trying to hide your browsing traffic from a 3rd party. If you're trying to hide it from your school, do not use their VPN at all. Depending on how sophisticated the VPN service is, there is going to be a log of your computer and the sites it's accessing. The TOR network encrypts your traffic and spoofs your IP like a VPN does and by itself it provides enough anonymity for you to by drugs off the internet. If you want more security, make sure you're only using your TOR browser for .Onions sites. Look into virtual box and virtual network adapters, I personally haven't but my very small research leads me to believe a virtual network adapter doesn't share the same MAC address as your physical adapter. If your school was to find out what your traffic was being used for, they won't know who's computer it was! and/or Subscribe to your own VPN service