In a changing technological society, creativity is recognized as the vehicle of economic and social growth. Although the education system has a central role in developing all students’ creativity, it is not often nurtured in schools. Several conditions are offered to justify this situation, among them: external pressures to cover the curriculum and succeed in standardized tests that generally require rote implementation of rules and algorithmic thinking; teachers’ tendency to teach similarly to the way they themselves were taught as school students; relating creativity to giftedness, and therefore avoiding nurturing all students’ creativity; teachers’ difficulties in assessing their students’ creativity and its development due to a lack of an available simple tool; and more. This paper is aimed at responding to the latter condition, suggesting a coherent and accessible tool or model for assessing students’ creativity and its development in the context of problem posing. The proposed model considers 4 measurable aspects of creativity-fluency, flexibility, originality and organization, and a total score of creativity that is based on relative weights of each aspect. Viewing creativity as relative, the scores for these 4 aspects reflect learner’s achievements in relation to his or her reference group. The proposed model has two flexible components—the first relates to teachers’ interpretation of originality, and the second relates to the weights they may wish to ascribe each aspect of creativity. In addition, it is suggested to provide learners with a graphical display of their scores and progress in order to enable them to refine their products in successive iterations. The examples in this paper are taken from mathematics; however the proposed model can be adapted to any other discipline.