The research aimed to measure the impact of the effectiveness of using a program based on cognitive flexibility theory to develop in-depth reading skills among prep school students.The deep reading program and teacher's guide was prepared based on the Duolingo based on cognitive flexibility theory. The observation card was prepared to measure the skill aspect of functional reading skills and thereasercher also made a trend scale towards in- depth reading to measure the extent of students; tendencies at this stage to learn and devlope in- depth reading skills using peogram based on the theory of cognitive flexibility, the second unit ("Egypt in our class") was taught in the first semester 2023/2024 AD. The research relied on the experimental approach based on semi-experimental design using the method of the two groups: an experimental group, and a control group, and the number of students of the two research groups reached (60 students) at Nasiria preparatory school of the east Zagazigadminstration in Sharkia Governorate.