The zone of proximal development is a well-known and frequently referenced term within cultural historical psychology. Nevertheless, it is rarely used in the concrete practice of assessing intellectual development. The majority of proposals for such assessment are based on a behavioral and psychometric conception of development. This study presents a Scheme for Evaluation of Intellectual Development based on the concept of the zone of proximal development and on gradual intellectual development. The Scheme was applied to 160 Mexican pre-school children from rural, suburban, official, and private kindergartens. The Scheme permitted us to determine the zone of proximal development by evaluating the children's level of external orientation during the solution of new intellectual tasks. Three levels of orientation through external help were established. The results showed that the majority of children from all groups managed to fulfil new tasks after receiving external help, which indicated the existence of their zone of proximal development. Differences were detected in the use of the level of help in all groups. Statistical analysis showed a significant correlation between the level of helping received, the degree of fulfilment of the task, and the children's socio-cultural group. The results permitted us to establish more precisely the zone of proximal development at pre-school age. We discuss how the concept of the zone of proximal development might be used in concrete psychological practice and research, instead of being only a well-known term at a declarative level.
