<![CDATA[Abstrak: Penelitian ini dilatarbelakangi pembelajaran Bahasa Indonesia dalam proses pembelajaran berpusat pada guru. Proses pembelajaran guru hanya mengajar menggunakan buku tematik tanpa ada bahan ajar penunjang lainnya. Guru lebih menerapkan keterampilan berbicara, menyimak daripada keterampilan menulis, sehingga minat siswa dalam mengembangkan kemampuan menulis berkurang. Tujuan penelitian ini dapat meningkatkan kemampuan berpikir kritis siswa melalui penggunaan bahan ajar menulis esai. Desain dalam penelitian menggunakan model yang dikembangkan oleh Borg and Gall, eksperimen one-group pretest-posttest design. Teknik pengumpulan data melalui observasi, dokumentasi,tes. Teknik analisis data untuk mengetahui kevalidan, kepraktisan, keefektifan bahan ajar dengan bantuan software SPSS 24 for windows. Hasil Kualitas produk bahan ajar pada aspek kevalidan bahan ajar sebesar 91% menjadi 95%. Kualitas produk aspek kepraktisan meliputi hasil respon guru dan siswa setelah digunakan bahan ajar memiliki persentase 82,5% meningkat  95%, Kualitas produk aspek keefektifan didasarkan pada hasil belajar siswa. Berdasarkan nilai derajat kebebasan adalah 48 dan nilai signifikansi adalah 0,05/2 = 0,025. Nilai tersebut dijadikan dasar acuan mencari pada ttabel, sehingga didapatkan nilai Ttable (0,05, 48) =2.01063. Dengan nilai thitung > dari ttabel maka dapat disimpulkan bahwa Ha diterima artinya terdapat perbedaan yang signifikan kemampuan berpikir kritis siswa setelah menggunakan bahan ajar menulis esai berbasis lingkungan dengan menggunakan model problem solving.Kata Kunci: Bahan Ajar, Menulis Esai, Berpikir KritisAbstract: This research is motivated by Indonesian language learning in the teacher-centered learning process. The learning process of the teacher only teaches using thematic books without any other supporting teaching material. The teacher applies more speaking, listening skills than writing skills, so that students' interest in developing writing skills is reduced. The purpose of this study can improve students' critical thinking skills through the use of essay writing teaching materials. The design in this study uses a model developed by Borg and Gall, a one-group pretest-posttest design experiment. Data collection techniques through observation, documentation, tests. Data analysis techniques to determine the validity, practicality, effectiveness of teaching materials with the help of SPSS 24 for windows software. Results The quality of teaching material products on the validity aspects of teaching materials by 91% to 95%. Product quality aspects of practicality include the results of teacher and student responses after use of teaching materials have a percentage of 82.5% increased 95%, Product quality aspects of effectiveness are based on student learning outcomes. Based on the value of degrees of freedom is 48 and the significance value is 0.05 / 2 = 0.025. This value is used as a reference base for looking at the table, so that the obtained value of Ttable (0.05, 48) = 2.01063. With the tcount> of ttable, it can be concluded that Ha is accepted, it means there is a significant difference in students' critical thinking skills after using teaching materials to write an environment-based essay using the problem solving model.Keywords: Teaching Material, Essay, Critical Thinking]]>
