Mnemonic Device:

• In the U.S. (and sometimes in the U.K.) the headmaster is called the Principal. To remind you that the ending of this word is “p-a-l,” and not “p-l-e,” remember he/she is your “pal.”

Explanation: to remember how to spell the word PRINCIPAL

Additional Information: Alternatively, the word principle means a personal code of conduct or fundamental truth.