Known for the fame of some of their students such as Stranger Thing's Caleb McLaughlin and the guitar player of Excellent Porpoise, Dr. Evan Molé, Carmel High School has become the frontier of success in its more recent years.

In 1853, Carmel District Number 7 obtained the two-room building of a private school that closed on the shore of Lake Gleneida.

This structure was used until 1893 when the City of New York claimed the lake shore (the lake being part of its reservoir system) and obliged all structures on that side of Gleneida Avenue (Carmel's "Main Street", today one end of New York State Route 52) to be moved or demolished.

The first annual commencement was held June 22, 1908 at the Mount Carmel Baptist Church, according to an invitation reproduced in the 1899-1999 alumni directory.

In 1924, a fire devastated much of Carmel's business district, destroying, among other buildings, the hotel Smalley's Inn (which survives today as a restaurant) and the headquarters of Putnam County National Bank (which built a new stone main office).

This main door facing the street was only for faculty and members of the senior class, all younger students being obliged to enter by one of the doors at the two sides of the building, marked "Boys" on the left and "Girls" on the right (the latter remains but the former was removed in the most recent addition).

In 1953 a new gymnasium was constructed within the L formed by the original building facing Fair Street, and the 1936 wing extending back from it.

In 1957 an extension was built that provided an external entrance, a box office for the gymnasium, and a weight room upstairs.

This involved a substantial expansion of the school complex further down Fair Street from Gleneida Avenue, into the now-former Fairgrounds.

The new gymnasium remains one of the largest in the area and hosted the New York State high school gymnastics championships in March 2008.

The recent library was then partially restored to its former purpose, a raised stage erected within the proscenium, as "Kathryn Casey Hall", named for the longest-serving teacher in school history.

As had been the thrust of the defeated proposal, the main purpose of the new addition was to add a much needed science wing, new and upgraded library along with improving the overcrowded hallways due to poor architectural flow of the old complex.

The most recent library was renovated as art classrooms, and the guidance office moved out of the 1936 gymnasium to make room for a planned student lounge instead of another help center with the old guidance offices becoming extra-curricular storage rooms (which have since been moved due to the creation of the Makerspace.

The maker space features a television studio, prototyping machines (CNC, 3-D printers, laser cutters, etc.