This study explored the types, frequencies and quality of student questioning based on three kinds of question-stems (detailed-stem, simple-stem, and no-stem). A questioning-supported thinking and learning system (QSTLS) was developed to scaffold stem-based student questioning. One hundred fifth-grade students participated in this study. Students were assigned to three groups: a detailed-stem group, simple-stem group, and no-stem group. Results show that the detailed-stem groups used more types (11) of questions, asked a greater number of questions (472) and asked questions of higher quality than both the simple-stem group and the no-stem group. The conclusion of the study is that online questioning is a useful learning strategy, and more specifically that detailed question-stems in particular help students to develop their questioning skills. This study also shows that with the assistance of question-stems, the QSTLS system can provide a student-centered and active learning environment for elementary pupils. (Contains 8 tables and 2 figures.)