The authors would like to sincerely thank participants including students, instructors and the school leader for their contributions to the study. The work was supported in part by Independent Research Project of Adaptive Learning for Primary School Mathematics of Central China Normal University (1100-30106190508), and by the Fundamental Research Funds for the Central Universities (Excellent Doctoral Projects, grant number 2019YBZZ039). *Corresponding author is Mingwen Tong, e-mail: tongliuwen@163.com.