This paper argues that design and usability issues are of great importance on technology-based implementation and evaluation programs, as they can have both a positive und a negative impact on teaching-learning processes. For instance, the quality of the design can aid the development of new reasoning skills on the one hand, and on the other it can affect the understanding of physical phenomena. From a pilot study conducted with the purpose of investigating how design and usability issues impact on the
mathematics and science teaching-learning process in secondary schools in México, we identify a number of problems that suggest the importance of considering these issues during the implementation of educational technology programs and during the evaluation of its outcomes, as these programs will ultimately determine the development of, for example, national curricula and national education policies.