This study investigates whether lesson plans created using ChatGPT, an advanced chatbot tool, improve students' math achievement in primary school. The research employs a pretest-posttest control group experimental design with 39 third-grade students (24 in the experimental group and 15 in the control group). The experimental group follows lesson plans prepared by ChatGPT, while the control group uses existing lesson plans. The study spans five weeks, covering 25 lesson hours. Academic achievement is measured through a multiple-choice test with 25 questions, each addressing a specific learning objective. Results show that students' math achievement significantly increased (d = 1.268) in the experimental group, but the difference between the experimental and control groups was not statistically significant. The findings suggest that using ChatGPT to prepare lesson plans can effectively enhance academic achievement in primary school math. Teachers are encouraged to integrate ChatGPT into their lesson planning, combining it with their own plans to maximize benefits and minimize potential drawbacks.This study investigates whether lesson plans created using ChatGPT, an advanced chatbot tool, improve students' math achievement in primary school. The research employs a pretest-posttest control group experimental design with 39 third-grade students (24 in the experimental group and 15 in the control group). The experimental group follows lesson plans prepared by ChatGPT, while the control group uses existing lesson plans. The study spans five weeks, covering 25 lesson hours. Academic achievement is measured through a multiple-choice test with 25 questions, each addressing a specific learning objective. Results show that students' math achievement significantly increased (d = 1.268) in the experimental group, but the difference between the experimental and control groups was not statistically significant. The findings suggest that using ChatGPT to prepare lesson plans can effectively enhance academic achievement in primary school math. Teachers are encouraged to integrate ChatGPT into their lesson planning, combining it with their own plans to maximize benefits and minimize potential drawbacks.