Present study investigated relationships between classroom overcrowding and the Turkish education curriculum (2006) in terms of the applicability of activity-based lower secondary Turkish education curriculum in overcrowded classes. In addition, the problems that occur in the teaching process and the sufficiency of time for the program were investigated. Qualitative research methods were used in the study. By conducting semi-structured interviews with 11 Turkish teachers of overcrowded classes, the effects of overcrowded classes on the applicability of the Turkish course curriculum was examined. To analyze the data gathered from teachers, categorical content analysis and QSR Nvivo were used. At the end of the research, it is observed that in accordance with the program, Turkish teachers have to work one to one with each student; that teachers find that the activities do not meet the objectives due to pressure of time resulting from overcrowding. Suggestions are construed such as doing group work to lower the effects of overcrowding.