You're right on the money about the "Field of Dreams" approach to the new school (If you build it - they will come). I understand the politics associated with this, but several schools in the area (Monroe Co. KY, Livingston, etc) swallowed up smaller schools in their counties and told everyone to deal with it. After a period of resentment, everything worked out. I doubt any of these people would go back to the way things were.
If Hermitage Springs loses 20-25 students from their high school (out of 125) they would cease to exist. Hopefully, all of those students would come to the new county school. With the issue of state/county taxes being what they are, it only makes sense to fund one school in the county - especially when they are as small as they are.