The application of digital technology in English smart classrooms in colleges and universities explores its impact on teaching effectiveness and students’ academic performance. Based on digital technology, this study examines the construction of English smart classrooms in colleges and universities and its impact on teaching effectiveness. The study collects and analyzes 590,000 teaching behavior data, uses a clustering model to explore teachers’ teaching behaviors, and constructs a set of algorithmic overlay methods for evaluating students’ performance. Through the six-month competent classroom teaching practice, the experimental group showed significant improvement in thinking ability, learning effect and achievement. Specifically, the experimental group’s mean values of verbal thinking, creativity, and critical thinking dimensions were higher than those of the control group by 0.663, 0.572, and 0.581, respectively, and the synergistic ability and problem solving ability were higher by 8.96% and 15.59%, respectively. In addition, the experimental group’s learning attitude, process participation and knowledge mastery were significantly improved, and their academic performance improved by 5.941 points during the experiment. These data confirm the effectiveness of the intelligent classroom in improving learning effect and achievement.