Abstrak: Analisis butir soal merupakan tahapan penting untuk memastikan kualitas instrumen evaluasi, namun praktik ini belum dilakukan secara sistematis oleh sebagian guru karena keterbatasan penguasaan statistik, kesiapan data, dan hambatan penggunaan perangkat lunak. Kegiatan pengabdian kepada masyarakat ini bertujuan memperkuat literasi asesmen guru melalui pelatihan analisis butir soal berbasis Classical Test Theory menggunakan software 3S-CTT. Mitra kegiatan adalah SMP Muhammadiyah di Kabupaten Lombok Barat Nusa Tenggara Barat dengan peserta 10 orang guru. Data praktik menggunakan paket soal pilihan ganda sebanyak 30 butir beserta respons siswa atau data latihan yang disiapkan oleh tim. Metode kegiatan disusun dalam tiga tahap, yaitu pra-kegiatan, pelaksanaan, dan evaluasi. Tahap pra-kegiatan meliputi koordinasi mitra, identifikasi kebutuhan, penyusunan modul, dan penyiapan data latihan. Tahap pelaksanaan mencakup sosialisasi konsep CTT, demonstrasi 3S-CTT, praktik input data, analisis, dan interpretasi output. Tahap evaluasi dilakukan melalui pre-test, post-test, observasi, checklist keterampilan, telaah output, dan diskusi reflektif. Hasil kegiatan menunjukkan bahwa pelatihan berbasis praktik membantu guru memahami indikator tingkat kesukaran, daya pembeda, reliabilitas, dan efektivitas pengecoh serta menyusun rekomendasi perbaikan butir. Kegiatan ini diharapkan menjadi model penguatan evaluasi pembelajaran berbasis data di sekolah mitra.Abstract: Item analysis is an important stage in ensuring the quality of assessment instruments; however, it has not been implemented systematically by many teachers due to limited statistical knowledge, data readiness, and software-related barriers. This community service program aimed to strengthen teachers' assessment literacy through item analysis training based on Classical Test Theory using 3S-CTT software. The partner was a Muhammdiyah of junior secondary school in West Lombok, West Nusa Tenggara, involving 10 teachers. The practice used a 30-item multiple-choice test package along with students' response data or training data prepared by the team. The program was organized into three stages: pre-activity, implementation, and evaluation. The pre-activity stage included partner coordination, needs identification, module development, and preparation of practice data. The implementation stage covered CTT concept introduction, 3S-CTT demonstration, data input practice, analysis, and output interpretation. The evaluation stage used pre-test, post-test, observation, skill checklist, output review, and reflective discussion. The results indicate that practice-based training helped teachers understand item difficulty, discrimination power, reliability, and distractor effectiveness and formulate item improvement recommendations. This program is expected to serve as a model for strengthening data-driven classroom assessment in partner schools.