In mathematics, situations calling for reconstruction of a transformation are frequent. In such situations, children aged 6 to 7 concentrate on the states, combining them in different ways. The present research aims to illustrate that difficulties and strategies observed with children 6-7 years old are not specific to this age level, but are also encountered by children up to age 12 and probably older. Numerous situations of reconstruction, ranging from easy to more complex, were prepared relying on criteria defined in a reference framework elaborated in the light of past research on problem solving. These items were presented to primary school children at all levels. Results reveal that the same errors reappear constantly, bringing to light important obstacles that interfere with the construction of a very fundamental concept in mathematics and sciences, that of transformation. (Author/PK)