Mr Black was once a nurse./Mr Black has been a nurse.

[diamondcutter]

“Help! Tom is choking on a peanut.” A girl yelled.
Mr Black, our math teacher, rushed to save the boy.
“Mr Black was once a nurse./Mr Black has been a nurse. He knows what to do.” Mrs White told us.
(Written by me.)
In this context, are these two sentences both appropriate?

 

[5jj]

I find the past tense more natural that the present perfect in that situation. I'd find 'used to be' even more natural.

 

[diamondcutter]

Do you mean that the present perfect in that situation is also acceptable?

 

[5jj]

I don't find it particularly natural.

 

[Barque]

Do you mean that the present perfect in that situation is also acceptable?

The present perfect in that sentence isn't natural. It'd work if the sentence was a little different.

Mr. Black has just completed a first-aid course. He knows what to do.