Hi
The email account is created by the school for school communications, I don't know of any organisations private or public that would let you take your business account and use it outside of that business. Best practice would be export your emails and contacts and transfer them to your new account whatever that would be.
Also if I remember your staff mail account uses USO credentials that may give you access to resources that you are not entitled to anymore as you do not work at that establishment and not to mention that horrible 4 letter word GDPR
So if you need an account that will follow you throughout your profession, I would suggest one of the big players i.e google msn etc...
good luck