A Carla Ventresca cartoon that came to me via Mar Rojo on Facebook:
It turns out that Mark Liberman posted this one on Language Log back on 3/18/07, with a nice discussion of the teacher’s incorrection (of fast to quickly) in the last panel. There’s another incorrection in the first panel, of shrimps to shrimp; as Mark noted, both forms are standard plurals for shrimp. (The remaining three corrections concern spelling and punctuation and are appropriate.)
Searching for this posting of Mark’s led me to more cartoons with English teachers in them.