Trainer version of the F-5. There used to be a bunch of them and T-37s at Williams AFB down the street from us.
IIRC, the F-5 is actually the fighter version of the T-38.
I think Williams AFB was the best training base. I went to UPT there and was in class 89-01. Some of the T-37 on the flight line had over 15,000 flight hours which resulted in many mid air mechanical problems. The T-38 is getting up there in age as well. The T-38 is a very unforgivable plane to fly and land.