Building a filter from sand and gravel is a classic science challenge.

Many adults believe Earth's shadow causes the Moon's phases. It does not. A lamp and a ball on a stick let children see the real reason in ten minutes.

Shake sand, gravel and soil in a jar of water and wait ten minutes. The layers that form are the start of the story of sedimentary rock, and children can see it happen.

Growing cress on cotton wool is an old classroom activity. Turned into a fair test, it teaches the most important idea in science: change one thing, keep everything else the same.

A red cabbage, some vinegar and baking soda are enough to show children how chemists tell acids from bases. It takes one hour, costs almost nothing, and children remember it.

A good science club does not need a lab or expensive kits. It needs one repeatable design cycle, cheap materials, a safe room and a leader who asks more than they tell.