Both have their value, both the process and the results. And given the immensity of scientific knowledge, you can only learn so much of it in a K-12 education, or even in college.
I don't think it's a priori wrong to teach students our current understanding of the world, without going into the details of how we came up with it. I also don't think it's wrong to add those details, but the more details you add, the less of the full picture you'll be able to present. And I definitely don't think it would be a good idea to teach children how we do science, without teaching them what we actually learned from doing it.
I'd also say that the reality of some of the process is extraordinarily boring ("we kept meticulous records of precisely where on the sky various stars were each night, and how their position changed, for a few hundred years, and tried finding a function that matched those numbers; for a few hundred years, we kept adding more and more circles to correct things, until Kepler came up with some ellipses"). And that for many children, learning history is already a huge bore, learning the history of science in addition would make science classes much worse. For others, the opposite is true.