In Second Class children have to learn the necessary skill of renaming in subtraction which can prove quite a challenge.

So as to make the process clearer they are given a variety of materials to represent the tens and the units. This allows them to physically see the ten being taken away and added to the units. Once they have the practical element well practised they are then able to transfer this skill into their written format. (Well at least that's what we are aiming for!!)