Boys game using girls. Involved encouraging or daring girls in skirts or dresses to do handstands so you could see their underwear.
John asks us to point out that in his experience as a pupil and teacher a cartwheel is quite different from a handstand. Handstands against a wall were quite popular with groups of both boys and girls. Girls would often tuck the hem of their skirt into to leg of their knickers, thus maintaining some decorum.
A cartwheel is an active process done sideways. Throwing yourself over side ways first onto one hand and the other and back on your feet. The body turns a full 360 degress. The arms and legs stick out a little like the spokes of a cartwheel.
(ed: ... errr... thanks... we'll call you ok?? <g>)