So recently my school has told us that from now on we would be monitored for everything we do online on there guest wifi, so my question is if I use a VPN on there network can they still see what i’m doing? I use Hotspot Shield Elite on my iPod and my laptop.
No they can't, as long as you ensure that your DNS traffic is also sent over the VPN.
However they will be able to tell that you're using a VPN if they look at the traffic.
How do I tell if the DNS traffic is also being sent through the VPN?
You could use a packet sniffer like wireshark and check that there is no DNS traffic (or other unencrypted traffic) on your network connection.
Or you could use something like this and check that the servers it lists are from your VPN and not the ones used by your network. https://www.dnsleaktest.com/