Moments with Y9 - started off at the classroom door, put the weakest kid in the class right at the edge of the door (furthest away from the hinge) pushing with one index finger. Strongest kid in the class on the other side of the door pushing with index finger about 2 inches in from the hinge. On go both push, weakest kid wins, so add another kid on the other side of the door.. and continue..got up to 4 kids on the strong side before our weak kid was even struggling.
Moments with Y9 - started off at the classroom door, put the weakest kid in the class right at the edge of the door (furthest away from the hinge) pushing with one index finger. Strongest kid in the class on the other side of the door pushing with index finger about 2 inches in from the hinge. On go both push, weakest kid wins, so add another kid on the other side of the door.. and continue..got up to 4 kids on the strong side before our weak kid was even struggling. Then had a ramp as a lever layed over a pivot on the classroom floor - I stand on the very short end, lightest kid in the class is lifted (carefully) with support on each side onto the other end...and lifts me
Another good use for stools (chair not biological) is for teaching moments. Get everyone to pick up their stool. No problems there - start explaining about turning force. Next get them to hold the stool at arms length. Most Y9 cannot manage this for more than a minute. Emphasis keeping arms straight, standing upright (no arching backs) and stool level. Ensure they know to put down stool if it hurts. Keep talking and asking questions while the stools are being held. I always join in and in 8 years have only been beaten once (Y11 who's saturday job was as a bouncer), but I do have strong shoulders (from lugging tonnes of marking around). You could give out prizes but I find the glory of lasting longest is sufficient (i usually "give up" a few seconds after the last one so they feel like they could beat me next time).