Trying to access a remote MySQL database

I'm trying to set-up access (for my IoT students) to a remote MySQL database that has been recording readings from our weather station.
I've written the NR flow and got everything working from my home using node-red-node-mysql.
Everything works fine - database updates and I can access it fine.
Also my friend in the USA can access the database just fine as well.

The problem comes when I try to do this via the school's network.
I can ping the MySQL server from the IT Room, so this sort of indicates there is a route to the server.
I've entered the various IP addresses into the Remote MySQL settings with my ISP to grant remote access.

I'm sure this is a networking problem with the school's network, but as I'm not familar with the intricacies of corporate networking I'm at a bit of a loss as to what to try next.
The error message I get in a debug node (at school) is "Error: Pool is closed" and "Database is not connected".

Any suggestions as to what I could check or try, would be appreciated.

Is the port on the server accessible via your network. I think it’s 3306 by default. Maybe a tool like nmap will help test it end to end

Thanks Dave - yes it is port-3306.
I'll ask the IT people to check it.

nmap -p 3306 ip-of-server

Should do it from your client end

Thanks Dave - when I said the IT people, I meant the IT people at the school.

I've just run the 'nmap' command on one of my RPi(es) and can see what the results look like - thanks.