This qualitative action research study. analyzed the contributio'1 of teacher-designed materials in the development of students' inquiry skills. For this study the skills selected were Observation. Prediction, Interpretation and Communication (OPIC). The study took place in a private school in Bogota with a sample of ten second graders. in the Science class. Six worksheets were designed based on the Second Language Acquisition principles focused on Problem-based learning approach. The data gathering instruments used were: students' artifacts with their self-assessment. field notes and focus group interview. Data was analyzed by using the grounded theory and the color coding technique. The findings showed that teacher-designed materials promoted self-construction of knowledge. understanding the socio-cultural context using sequenced worksheets that favor students' preferences and provided strategies to achieve communicative goals and independent practice supported by feedback. Problern-based learning strategies to solve problems benefited identification ,rnd description of elements and situations to find needs; comparison leaded to suitable outcomes on problems; and inquiry skills were enhanced through observation and prior knowledge for accurate prediction and appropriate interpretation of data that supported different ways of communicating results.