According to Thomas Marvel, the 1924 design of the Arecibo High School façade is distinctly Nechodoma with the two pilasters framing the front entrance topped by spheres.  These characteristics, states Marvel, are in the same spirit as the Larkin Building in Buffalo, NYdesigned by Frank Lloyd Wright.

This design is also attributed to Adrian C. Finalyson who worked for the Interior Department until 1921 and designed many schools and public buildings all throughout the island during his tenure.  The Arecibo High School is included in this edition of the Architectural Record which lists the work of Finlayson in Puerto Rico starting on page 137.

Marvel states that this Nechodoma design was in 1924.  The writing on the vintage picture below states "Memories of a day trip to Arecibo High School 1921".  This tends to indicate the design to prior to 1924 therefore most likely Finalyson's, who was the Interior Department Architect until precisely 1921.  

The school, located at Ave. José De Diego corner Calle Adraino Gonzalez, closed down in 2000 and the building is now vacant.