From Wikipedia:
Castle Heights Military Academy was a military academy in Lebanon, Tennessee.
The Academy was founded as Castle Heights School in 1902. In 1918, it became a military preparatory school. The school ceased operations in 1986 in the face of declining enrollment. Its buildings have been restored and now the main building serves as the Lebanon City Hall, Lebanon Museum and History Center.
This building is stop #13 on the Historic Lebanon Driving tour. Here is the text from that brochure:
David E. Mitchell and I.W.P. Buchanan opened the Castle Heights School in 1902. Mitchell had just been named president of Cumberland University where Buchanan was professor of mathematics. Their idea was to create an environment unlike any other preparatory school. Students who did not live in town were required to board at Castle Heights.
The school had ninety-four boarding students and fifty-nine day students its first year. In 1917, the school changed into a military academy. Castle Heights Military Academy (CHMA) closed its doors forever August 13, 1986.
For eighty-four years the school had shaped boys, and girls beginning in 1973, but was not able to carry on, hindered by a lack of enrollment and adequate financing.
The remaining buildings of the former campus were added to the National Register of Historic Places as a Historic District in 1996.