A method, a device and a computer readable storage medium for conducting a customized educational session to assess or teach a student by selecting contents for presentation to the student based on descriptors associated with questions and/or incorrect responses. The contents presented include both questions for assessing the student's knowledge state and intervention materials for teaching the student. The descriptors associated with the questions and incorrect responses are analyzed using one or more psychometric models to estimate the deficiency or weakness of the student's learning. Next contents are selected or created based on the estimated deficiency or weakness in the student's learning.