Authors have been performing the educational practice with a text communication tool "iConversation" since fiscal year 2012. iConversation is a web application program that a student can send the text messages addressed to a teacher just before the end of a lesson. The teacher can confirm the each student's recognition concerning state of his/her understanding and willingness to learn, the question about lesson content, and the demand for lesson progress from each student's text messages. Thus, the teacher can add the explanation and the encouragement tailor for each student's understanding and willingness, answer to the each questions, and improve the teaching material and lesson design. However, although the teacher's workload of text communication with students should be made a minimum achieving the effect of teacher's responses, it is not clarified the cases of the content that should be paid attention, the teacher's responses, and the their effects. In this study, the cases are guessed based on the text message data of iConversation.
