St. Elmo trailed at halftime, but used a third-quarter run to get ahead of Altamont, and the Eagles would eventually prevail, 43-34, during Friday's night regional championship game in Altamont.
Junior Connor Beasley had a double-double to lead St. Elmo to its second straight regional title. With the win, the Eagles will play Woodlawn at Red Hill High School on Wednesday night.
This will be the second straight season those teams have met in the sectional tournament.
St. Elmo's win was the fourth against Altamont this season and gives the team a 22-7 record.