For information on the Keystone Pediatrics Health Center at the Chambersburg Area Senior High School, click here. Primary Sidebar. Office Address. 830 Fifth Avenue Chambersburg PA 17201. (717) 709-7950 (717) 263-8898. Office Hours. monday 8:00am to 5:00pm. tuesday 8:00am to 5:00pm. wednesday 8:00am to 5:00pm..