This chapter focuses on the comparison of the conventional linear force-based method with the advanced nonlinear deformation-based method that are commonly preferred to investigate the seismic performances of the existing RC school buildings. School buildings which have different structural characteristics and RC infill wall index are generated from an existing school's layout plan. During the nonlinear dynamic analysis, seven recorded earthquake motions which are scaled in accordance with the Turkish Earthquake Code are employed. Seismic performances of the school buildings against the two different earthquake hazard level are evaluated considering not only various RC infill wall indexes but also different material strengths and number of stories in terms of limit states specified in the code. In order to determine the most appropriate method related to material strength, floor level and RC infill wall index for the seismic strengthening of the existing RC school buildings, the obtained linear forced and nonlinear deformation based analyses results are compared to each other.