This study examined how six Singapore teachers approached the design and implementation of a unit of work (topic) to demonstrate exemplary classroom practices that engage learners and use ICT in knowledge-generative rather than presentational activities. After a reflection and feedback session on the first lesson observation involving the researcher and the teacher, the teacher redesigned the lesson to enhance ICT use and involve students more actively in their learning. Our study revealed that there is a difference between students' physical engagement and cognitive engagement in a task and that the teacher, as a designer of the learning environment, needs to make explicit the cognitive processes involved in using the tool to ensure students' effective use of ICT. The teachers' understanding of what constitutes effective learning and their roles in students' learning determine how they design the learning environment. In essence, it is the teacher's skill in managing the "tripartite" partnership of IT tool, learning task, and teacher support that brings about higher levels of student engagement.