Teaching/learning evaluation at school is discussed as collaboration between teachers and pupils during scientific knowledge searching in their everyday activities. Based on a dialectic conception of knowledge, we reject the mere grading evaluation which is habitually done at schools and suggest that the critical thinking should play the central role in teacher-pupil-knowledge interaction. Therefore, evaluation should focus on the construction dynamics of meanings. Experiments of this evaluation concept with the teaching of university chemistry have led to some good results: more participation of the students during classes, more and better critical thinking, and thus a more effective teaching. The major difficulty found was to break the tie established by pupils between class activities and grading, since they are conditioned by a classification type of evaluation.
science teaching; school evaluation; dialectic conception of knowledge.