What correspondence school did X the Owl receive assignments from?

X the Owl received assignments from the Owl Correspondence School.

The school was a recurring part of X’s character in the Neighborhood of Make-Believe. Curious, bookish, and eager to learn, X regularly awaited lessons delivered by mail or through visiting instructors. The school’s name was often shortened to OCS, and its lessons covered subjects ranging from poetry and music history to trees, safety, and “people-watching.”

The correspondence-school idea fit X’s identity as an enthusiastic learner living in a tree’s knot hole. It also gave the program a playful way to introduce educational themes without placing the characters in an ordinary classroom. Packages and lessons could arrive unexpectedly, sometimes delivered by Mr. McFeely or carried into the story by another neighbor.

The invented school is easy to confuse with one of the fanciful alternatives in the answer choices, but “Owl Correspondence School” is the established name. X’s cousin, Mary Owl, is portrayed as one of its instructors.