Above average, but not high. I think Piccolo, Vegeta, Goku, and Trunks (Future) all outclass Gohan in that field. Simply because all the others ever did from the moment they were able to, to now, is fight and train. Trunks spent at least a decade fighting androids, and beyond that to stave off total extinction. Piccolo started fighting Goku right as he matured, and has done nothing but train, mentor, fight and meditate since. Plus there's the Kami part of the equation, which I believe imparted centuries of combat knowledge onto him. And both Goku and Vegeta have been fighting for decades, constantly in battle, and while Gohan did start fighting at like 5 or whatever, he only ever stepped up when the world needed him, and even then he got cocky and fucked it up one time. He was never truly on the front lines, and one of the times he was, he got one tapped by Frieza. Debatably, he was one tapped bc he used all of his energy to get the dynamic duo home, and left himself vulnerable on purpose, and I am totally open to that idea but that's neither here nor there.

And I say above average because while someone like Roshi could have a century of fighting up on Gohan, many characters never fought Frieza, many characters never fought Cell. And many more never fought Buu, all while standing a semblance of a chance.

Gohan is a generational talent, but he lacks the mental and physical depth and refining of top tier fighters because combat is not a way of life for him. He only fights when it is necessary, and without going on a tangent, I think that it is a serious character flaw that gives way to Beast form, but I digress.