Metasploit Exploitation

I am using metasploit now with some succes. I created a payload with Veil-Evasion which doesn't get discovered by my AV and it works fine. I tested it with some computers in my own network and with a friend of mine it still worked when I used my public IP instead. However I wanted to experiment with this even more and tried it on the computer science computers at school with the permission of the teacher responsible for that classroom. This time it didn't work even though I tried like 5 computers. I am not that experienced and therefore I am not completely well informed about the network that computers function in at for example school. Does anyone know how to solve this?

Do you think the firewall of the schoolnetwork might be preventing my payload from connecting from inside the schoolnetwork to the outside which is my own private network and if so how do I solve it?