Southwestern Educational Society ("SESO") is a private, English language school in Mayagüez, a western municipality in Puerto Rico that was founded in 1973.

Southwestern Educational Society (Sociedad Educacional del Suroeste) was founded in 1973 as an independent, nonprofit organization to achieve these goals.

SESO is an independent, nonprofit, English language school serving the children from local, U.S. and international families of the area.

The bass player of one of the most successful Puerto Rican rock bands Sol D'Menta, Erick "Jey" Seda is a mathematics teacher at SESO.

SESO is accredited by the Middle States Association of Colleges and Schools and licensed to operate by the General Council of Education of Puerto Rico.