"Buckwheat & Darla" joke

Buckwheat & Darla were in school, and the teacher asks Darla, "How do you spell 'dumb'?"
Darla says, "D-u-m-b, dumb."
The teacher says, "Very good, now use it in a sentence."
She says, "Buckwheat is dumb."
The teacher says, "Now spell 'stupid'."
Darla says, "S-t-u-p-i-d, stupid."
The teacher says, "Very good, now use it in a sentence."
Darla says, "Buckwheat is stupid."
Then the teacher calls on Buckwheat and says, "Buckwheat, spell dictate."
Buckwheat stands and says, "D-i-c-t-a-t-e, dictate."
The teacher says, "Very good, now use it in a sentence."
"I may be dumb and I may be stupid, but Darla says my dictate good!"