The purpose of the study is to investigate the effectiveness of Adey and Shayer model for accelerating cognitive development of Mathematics teaching in developing Mathematical sense and decision-making skills among second –year preparatory stage pupils. The subjects of the study consisted of two groups from second- year preparatory school pupils in Benha educational administration, Qlaubia governorate. They were divided into an experimental group (N= 49 pupils) from El-Kuds El-Sharif Preparatory school for boys (taught by using Adey and Shayer model and control group (N= 55 pupils) from Hamza Ibn AbdelMotalb preparatory school for boys (taught by regular method) in the second semester of the academic year 2018-2019. The instruments of the study included a mathematical sense test and decision making scale . Both instruments were applied before and after the experiment. Results of the study revealed a statistically significant difference (Less than or equal 0.01 level) between the mean scores of the experimental and control groups in mathematical sense and decision making in favor of the experimental group. In addition, there is a statistically significant difference (Less than or equal 0.01 level) between the mean scores of the experimental group pupils in the pre and post administrations of mathematical sense and decision making in favor of post administration for the experimental group. The study presented number of recommendations and suggestions for further research such as presenting training sessions for teachers on how to teach through using Adey and Shayer model and developing mathematical sense and decision-making skills among pupils. It focused also on presenting the mathematics lessons in the form of activities to help in developing mathematical sense and decision-making skills among pupils.