This study aims to evaluate the practicality, validity, and effectiveness of learning tools for the ecosystem topic in MTs (Islamic Junior High School) students. Learning tools include syllabus, lesson plans, teaching materials, student worksheet, and critical thinking assessment sheets. The research model used is the Tessmer model which includes 1) self-evaluation, 2) expert testing, 3) individual testing, 4) small group testing, and 5) field testing. The data analysis technique used is descriptive quantitative. This type of research data is validity data including content validation of the expert team and students, practicality data, and effectiveness data. This type of research is development research. The research was conducted at MTsN 6 Banjar. The research subjects consisted of the subject of validation of 5 experts, individual trial subjects of 3 students, small group trials consisting of 10 students and field testing consisting of 64 students. The results showed that the learning tools developed were valid, practical and effective. Valid based on the results of the validation of 5 experts who are categorized as very valid. Practical use because the model teacher and students are able to carry out learning activities well and students give good responses. Effective based on: 1) the learning outcomes of students in the experimental class have exceeded classical mastery. 2) Critical thinking skills include formulating problems, providing reasons, grouping, analyzing and formulating conclusions in the experimental class in the good category. The results of the comparison between the experimental class and the control class through the Whitney Test found a significance value below 0.05 indicating that the tools developed and applied to the experimental class were able to train students' critical thinking skills better than the control class. 3) The mastery of the critical thinking skills indicators of students in the experimental class is categorized as good. Individual mastery in the experimental class exceeds the 75% limit which means that learning mastery has been achieved classically.