The phrase, six of the best’s, origins are unknown. It is known to have been used in England from around 1700 onwards and means six sharp flogs with a cane or the hand, generally on the posterior. Mainly heard in ultra-British twenties and thirties English private schools, (often in Billy Bunter), it became something of an institution. In the great comedy series “Blackadder” or specifically “Blackadder Goes Fourth,” Lieutenant George expects to give the Kaiser “A real British Flogging, six of the best, belts off, trousers down.”
In it’s day to be sent for “six of the best” might have been seen as almost an initiation rite. Nowadays it is heard in the context of “you young-uns have it so easy nowadays, back in my day we was sent for six of the best for so much as smudging an inkblot, ah, thems were the days.” Since corporal punishment has been made illegal in all schools in England the phrase is seldom heard for anything but comic value