I read this book sometime in the 80-84 time frame, possibly slightly earlier and no later than 1985.

I only recall that a boy was living in a village and he was training at various occupations – mining chalk (?) possibly from some chalk downs, studying astronomy and such things.

He at some point runs away or gets away and falls into some sort of underground crypt where he encounters the remains of some warrior lying there with a green stone axe on its chest.
He takes the axe….and that’s the last I remember.