The document created by Leland S. Congdon Sr. (1920 - 2011) found at the link above summarizes the evolution of schools in Clarendon.
The cover photo is a small segment of the 1771 William Cockburn map of Socialborough which was the predecessor community that substantially comprised what is now Rutland Town & City and the north central part of modern day Clarendon. You can see in the lower central part of the map that there was what was likely the first school in Clarendon given that area was first settled in 1768. That school would have been in the vicinity of what became Middle Road roughly a quarter mile south of Moulton Ave.
Note that measurements on the map are in chains (1 chain = 66 feet).