UPDATE 1 - July 2016: We know that the English dub for "The Blight Before Christmas" and "The Flipper" are still missing, but the Latin American Spanish dub (La mascota de la clase) has next to no clips. The only footage found so far is a clip of "The Blight Before Christmas" (lol we found a clip), an "Up next" bumper from Disney Channel, and the opening theme in Spanish. The dubbing info for the Spanish Dub is down here: http://es.doblaje.wikia.com/wiki/La_Mascota_de_la_Clase
UPDATE 3 - August 7th, 2016: I managed to get the full episode "The Blight Before Christmas" from "Navidad Clásica" on YouTube after it was sent to me via MEGA. The episode is now available on Dailymotion (albeit low quality and mirrored).
UPDATE 4 - September 13th, 2016: As of August 31st, reruns have stopped airing.
UPDATE 5 - March 15th, 2017: As of March 8th, the show is back on at 11:30 in the morning on the weekdays.
UPDATE 6 - November 12th, 2019: Teacher's Pet is available on Disney+ with a Spanish audio track, meaning that the dub is found.