Earl R. Knorr, 80, formerly of Springfield, Delaware County, a principal at Springfield High School for 20 years, died of heart failure Tuesday at White Horse Village, a retirement community in Newtown Square.

Mr. Knorr taught social studies at Unionville and Kennett Square High Schools for 13 years. He then served as assistant principal and principal at Kennett Square from 1963 until 1970, when he became principal at Springfield.

He established the Festival of the Arts at Springfield, and the school's theater is named for him.

While he was principal, said his wife, Mildred Kent Knorr, he used vacation time to be an accreditation evaluator for the Commission on Secondary Schools of the Middle States Association of Colleges and Schools. He was past president and served three terms on the association's board. After retiring from Springfield in 1990, he continued to evaluate secondary schools in the mid-Atlantic region and abroad until five years ago. He was committed to quality education, his wife said.

Mr. Knorr graduated from Eddystone High School, and earned a bachelor's degree in secondary education from West Chester University and a master's degree in American studies from Temple University.

He enjoyed tennis, travel, fine food, Notre Dame football, and acting. He had major roles in productions at the Kennett Little Theater, his wife said, and could quote many passages from Shakespeare.

He and his wife were longtime subscribers to the Philadelphia Orchestra, the Walnut Street Theater, and the Opera Company of Philadelphia.

He was a volunteer at the Newlin Grist Mill in Glen Mills, at Brandywine Battlefield in Chadds Ford, and at Carpenter's Hall in Philadelphia. He also was a leader of a great books discussion group.

In addition to his wife of 57 years, Mr. Knorr is survived by a son, Kevin; a daughter, Jennifer Harden; and two grandchildren.

The funeral will be at 11 a.m. today at Church of the Redeemer, where he was rector's warden, vestryman, and lay reader, 1545 W. Springfield Rd., Springfield. Burial will be in Philadelphia Memorial Park, Frazer.