The study sought to investigate the effect of a suggested program based on Problem Space Theory for assessment to develop critical reading and writing skills of EFL second secondary stage students.  The sample consists of 30 students and three raters from Al Abaseya and Al Basateen Preparatory / Secondary Institutes for Girls, Al Azhar Al Sharif institutes, Cairo Governorate. The researcher applied one group quasi-experimental design. A blueprint, prepared by the researcher, is given to the students as an introduction to the suggested program. Quantitative data is obtained from the pre- posttest and the test is assessed by the integrated critical reading and writing checklist prepared by the researcher. The qualitative data is obtained from the student interest inventory, a questionnaire for the participant teachers, observation card and unstructured interview with the participant teachers. Triangulation of the qualitative analysis emphasized the conclusion of the posttest scores. That is, there is a statistically significant difference between the mean scores of the research group in the pre and post-test administration of the overall and the sub-skills of the critical reading and writing skills in favor of the posttest scores. After testing the validity of the hypotheses, the findings revealed the effectiveness of the suggested program on developing the critical reading and writing skills of the EFL second secondary students.