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 highchallenge 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 smallgroup 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. R eading comprehension is a critical skill essential for access to the broad curriculum and long-term academic success (McNamara & Magliano, 2009). Classroom instruction in reading comprehension often takes the form of teacher-led, small-group reading and discussion of a text, a format commonly referred to as guided reading (Ford, 2015; Fountas & Pinnell, 2017). In these sessions, the teacher works on a text with a small group of students, typically of similar reading ability (Fountas & Pinnell, 2017). Central to the concept of guided reading, and other teacher-led reading comprehension instruction, is the use of questions to check comprehension and encourage deeper thinking about the text and to scaffold understanding of challenging texts and discussion within the group (