Sorry this is so sketchy. I read the story in a fiction anthology collection in the 1970s when I was in elementary school. It's about an unusual boy who joins a school, apparently very withdrawn and silent. He may be from outer space, as the reader is eventually led to surmise. One intriguing thing he does is draw a very elaborate geometric pattern on his desk with a thick ink-like substance, and I think he attaches earphones to it. His teacher tries them on one day and think he hears something! His written English is poor and I recall he writes the word Library as "liby", or something similar. Toward the end he meets an adult who seems similar to himself, and asks him "where's your ship?" My memory is so vague that the last part may not even be real, but I appreciate anyone's indulgence.
This is The Substitute by Zenna Henderson. I read it in the anthology The Anywhere Box.
The boy is called Keeley and his spelling is odd. He does mis-spell library but spells other more complex words perfectly.
"Hasn't he been doing any work at all?" Bennett's quiet voice broke in.
"Practically none. Here. I brought today's papers to show you. His spelling. I gave him fourth grade words since he barely reads on that level and would be lost completely on seventh grade words. Look, beecuss. That's because, liby. That's library. Well, just look at it!"
Bennett took the dirty, tattered piece of paper and tried to decipher the words. "Pretty poor showing," he murmured. "What's this on the bottom. Vector, Mare Imbrium, velocity. Hm, fourth grade spelling?"
The description of the pattern with earphones is:
Bennett looked at Keeley's desk. The whole table was spiderwebbed with lines drawn in a silvery ink that betrayed a sort of bas-relief to his inquiring fingers. At irregular intervals, blobs of gum or wax or some such stuff was stuck, mostly at junctions of lines. There were two circles on the desk, about elbow-sized and spaced about right to accommodate two leaning elbows. Each circle was a network of lines. Bennett traced with his finger two fine coppery wires that were stuck to the side of the desk. Following them down into the desk drawer, he rummaged through an unsightly mass of papers and fished out two little metallic disks, one on each wire.
Bennett examined the metal disks. "Let's try this out," he said, half joking. He slid into the desk and leaned his elbows in the circles. He pressed the disks to his ears. A look of astonishment flicked across his face. "Hey! I hear something! Listen!"