How do teachers elicit and sustain students' interest and engagement in science lessons? This paper answers this question in the context of Bhutan, where students' performance in science is low compared to other subjects, and where falling levels of interest in science are a concern. Like other countries in the Global South, a large proportion of science lessons are delivered through interactive lectures. Data were generated from observation of 78 grade 6, 8 and 10 science lessons at a Bhutanese middle secondary school, complemented by interviews with 4 students in each grade and their teachers. Teachers' questioning techniques were key to interactive lectures that students found interesting and engaging. Using Krapp's Person-Object theory of Interest (POI), questioning practices were analyzed in terms of cognitive challenges, autonomy, cognitive dissonance, and novelty. This paper offers new insights into science pedagogies for contexts where interactive lectures remain common pedagogical practice.