The school was Oliver Goldsmiths Camberwell & I remember 3 boys & 1 girl smacked over Teachers knee in this manner.
One boy was stupid enough to get all 7 wrong to see if he got 7 smacks, 7 plus, as per our skipping rhymes, one for luck, two for luck & 3 for the old mans coconut!
The smacks were by hand & no clothing removal was needed to ensure pain and a lesson taught!
As for reading, you knew Teacher had you under observation if she came from behind her desk & sat in her chair just behind & beside you as you were stood up reading to the rest of the class,
in the front. 1st public warning for ditherers and dissidents came when she drew even closer, 2nd when the leg of your shorts or the hem of your skirt was raised slightly at the back, and Misss flat hand pressed firmly on the back of the slappable leg.