I have been using my school wifi to download and goon social media, recently my IT teacher said that anyone who uses it will be tracked with their mac address and other ways and find out who is using it
Is this true? Will they know what am downloading and doing? And will they track me?
More than likely yes on all accounts. When you connect to their access point they will be able to see your MAC, IP address, source and destination traffic at least. Some organizations also have the ability to decrypt SSL/TLS (encrypt) traffic. If you are connecting to anyone else's wifi you have to take into account that they sit between you and your destination on the internet and assume that they can see everything you can see (this also depends what level of proxy/content gateway they are using as well).
It's impossible for us to know since we do not how sophisticated their monitoring ability is. There are some content gateways/firewalls that can flag VPN traffic and onion routing protocols (i.e., TOR), but we have no idea what they deployed in their network.
That being said, it would be improper for anyone here to recommend ways to bypass security controls on another organization's network.