Abstract
The purpose of this study was to use the concepts of Montessori method in the experimental teaching design for these three elementary school students diagnosed as learning disabilities in mathematical learning. The teaching material came from the arithmetic of Montessori methods. The researcher adapted the multiple baseline across subjects of single subject research to design the experimental procedure and to collect data. The effectiveness of Montessori method was determined after this two months’experimental teaching. This teaching content included Montessori’s sensory and addiction education. The literature review contain the mathematical performance of the learning disabilities, the classroom teaching of Montessori Method in mathematics, and the evaluation of the mathematic problem-solving system. The data collection of this study was to count the percentage of right answers in order to describe the learning performance of these three subjects. The result of this study showed the mathematical abilities of these three students were improved.