When I was in HS Band and Orchestra almost 50 years ago all our music came in a set with full conductor's score as well as individual parts for the instrumentalists. I'd assume this would still be the case, although I have no idea what the cost would be (as I remember they were pretty pricey back then).

I suppose it depends on whether a publisher figures a profit can be made by supplying the score and parts, but I'd think most mainstream works would probably be available that way.