With the ability to provide feedback and assistance, humanoid educational robots have been proven effective in assisting students to overcome learning challenges and enhancing individual learning outcomes. However, the strength of humanoid robots in promoting social and emotional skills has not been well investigated. Socially supportive behaviour can contribute more to students' learning engagement than knowledge transfer. This study focuses on the design of humanoid robots to engage students from functional and affective perspectives. To this end, a pilot test is conducted on 64 primary school students in Hong Kong, comprising a control group (N = 33) and an experimental group (N = 31). Questionnaires, observations, and language proficiency test are done to ensure the validity of the findings. The results show that the experimental group, which learned with the humanoid robots, significantly improved their behavioural engagement (+ 13.24%), emotional engagement (+ 13.14%), cognitive engagement (21.56%), and intrinsic motivation (12.07%). The impact of utilizing humanoid robots in education is elucidated through the lens of the self-determination theory (SDT), which pertains to students' learning motivation and engagement. These findings can provide valuable insights into the development of more captivating humanoid robots for extensive learning purposes.