The authors examined teachers' (N = 19) use of different question types during small-group comprehension instruction for 6-11-year-olds (N = 115). The authors tagged the corpus of 40 hours of guided reading sessions to enable computer-based searches for syntactic forms of questions. Teachers frequently asked high-challenge "wh-" word questions (e.g., "How does that fit in with what you just read?"), and this was more pronounced in schools located in regions of low socioeconomic status, a finding associated with recency of completion of teacher training. Students' responses were more linguistically complex when teacher questions comprised a high frequency of high-challenge questions, particularly "wh-" word adverb questions (predominantly "why" and "how"). These findings applied across the wide age and ability range of the sample, indicating that high-challenge questions are effective in small-group comprehension instruction for students in different age groups and at various levels of reading ability. The authors conclude that teachers benefit from being informed about the effect of various syntactic forms of questions, particularly the nuances of "wh-" word questions. The findings also highlight the advantages of using corpus search methods to examine the influence of teacher question-asking strategies during classroom interactions.