Dutch research has revealed that pupils at special schools for primary education can best learn arithmetic using one specific strategy. When adding and subtracting with numbers less than 100, these pupils make least mistakes when using the so-called threading strategy (for example, 65 - 23 = 65 - 20-3). Bauke Milo investigated how children with learning difficulties can best learn to add and subtract numbers less than 100. Arithmetic lessons using modern methods challenge pupils to come up with their own solutions. However, children with learning difficulties require a different approach. The skills expected in modern arithmetic education are out...