Dr Lai Meng Choo of the Centre for Excellence in Learning and Teaching of the Education University of Hong Kong had offered consultancy support service to St. Francis’ Canossian School on enhancing the school-based model of lesson observation and evaluation in 2019-2021. In the final sharing session, the teachers demonstrated a Chinese lesson on “Descriptions of Human portraits” and a Mathematics lesson on ‘Understanding the equal division of fractions”, providing teachers of the whole school an opportunity to comment on the effectiveness of the lessons from different perspectives; 1) judging the value of the lesson from the perspective of the selection of the ‘Object of Learning’; 2) judging the accuracy of the ‘Critical Features’ from the perspective of the subject content and students’ learning difficulties; 3) judging the strengths and weaknesses of the lessons from the perspective of adopting ‘Variation’ in the instructional design; 4) judging the classroom interactions and learning outcomes from the perspectives of assessments. To ensure the quality of the open lessons for the whole school, Dr Lai had co-planned the lessons twice with all the Chinese and Mathematics teachers respectively and student interviews were conducted after lesson observation so that teachers participating in the lesson observation could evaluate the effectiveness of the lessons based on the evidence of student learning.