This is postmarked 1956. It was published by Blackburn News Agency. The company was located on Boone Street, started in 1945 by Joseph D. Blackburn and his wife, both former school teachers in Charlotte. In 1960, they were servicing over 200 newsstands in the area with paperbacks and, obviously, postcards (Kingsport Times-News). It was printed by Curt Teich in Chicago.
Blackburn had a series of postcards of Kingsport. This is noted as B-27.
Dobyns-Bennett High School. This card, luckily, was printed by Curt Teich in Chicago and I can read the inventory number to tell when it was printed: 1951. The photo may have been taken in 1950. Again, the coloring is false (the photo was taken in black and white), though the application at the printing company hewed to notes taken by the photographer. Any automobiles or other distractions may have been edited out.
It was published by Blackburn News Agency in Kingsport.
The linen finish on the front, applied during the printing process, is rather heavy handed. I know the company experimented with different linen patterns at times, so this may have been a new plate.