Section 3.2 Postnatal development

During the school-age years, children’s thinking becomes more logical and organized, especially when dealing with real or concrete information. Although they are not yet able to reason abstractly, they show significant progress in understanding and processing tangible facts and experiences. One key development is the improvement of classification skills. Children in this stage can sort and group objects based on multiple features such as shape, size, and color simultaneously. By around age 12, most children are capable of classifying items using two or three characteristics at once, demonstrating a more advanced and flexible way of thinking.

During the school-age years, children develop an understanding of conservation, meaning they realize that an amount remains the same even if its shape or appearance changes, as long as nothing is added or taken away. This cognitive milestone reflects their growing ability to apply logical thinking to concrete situations. Their understanding deepens over time, with conservation of substance and mass typically grasped by around age 10, and conservation of volume understood by about age 11 or 12.

Children use logical arguments to explain conservation:

•    Compensation: “This container is taller but thinner, so it still holds the same.”

•    Identity: “Nothing was added or taken away, so it’s still the same amount.”

•    Reversibility: “If I pour the water back, it will look just like before.”

•    Concrete thinking: At this stage, children can only apply logic to things they can see or touch (concrete objects). As they get older, they slowly start to understand abstract ideas (which are part of the next stage — formal operations).