Mr. Pilchard calls in sick. "My head is aching. I'm nauseous and I don't think I can come to work today."
By chance, the principal has picked up the phone. "Mr. Pilchard, you are a master teacher, one whom the boys and girls could certainly not do without. I'd hate to send a mediocre sub in your place."
"I'm going to tell you my secret," continued the principal. "Whenever I'm not feeling up to par, I simply have sex with my wife. It completely refreshes me, and I feel like a new man afterward. It never fails. I'll understand if you're a little late, but please do come in."
Several hours later, Mr. Pilchard arrives at work. The principal heartily greets him.
"So, Mr. Pilchard, did you take my advice?" asked the principal.
"Why yes I did, sir," replied Mr. Pilchard, all smiles. "And may I add, you have a very lovely home."
With apologies to Schoolgal