Rather than sticking the balanced chemical equation for aerobic respiration up on the whiteboard, allow KS4 students to ‘discover’ it themselves by using Molymods.
Start by drawing a glucose molecule on the board and get each pair of students to make it using Molymods. Then give each pair of students 10 oxygen molecules and ask them to completely oxidise the glucose molecule by converting it to water and carbon dioxide using as many oxygens as they need.
When they are done let them count it all up. One glucose has turned into six waters and six carbon dioxides. They will likely have forgotten how many oxygen molecules they used but just ask them to count how many are left over!