To pick your elementary school teacher press A when the Mr. Turtlepedia appears. But do it quick. If you leave one teacher for too long it will stick and you won't be able to change it. Press B to confirm your teacher. Mr. Turtlepedia is the smarts teacher, Miss Flower is the style teacher, and Mr. Canvas is the kindness teacher.
As for your other question, there is no job as the matchmaker. But it would be so sweet if there was, maybe it will be on the V4.5! Who knows?