When I was a child, I couldn’t spell the word “principal.”   I kept getting confused with its homonym “principle.”   I remember Mr. Vay, the friendly head of our middle school, set me straight. He said, “You want to end the word with P-A-L because I’m not just your principal, I’m your pal!”   And somehow that corny little mnemonic device did the trick.   Today’s principals have come a long way since Mr. Vay.   Many…