Professor Dr. Wolfgang Klafki, an educational researcher of West Germany, advocated about 25 years ago the concept of "Doppelseitige Erschliessung", which means a phenomenon of teaching and learning in which teachers can teach learners the principles of ways of learning on the one side while learners can gain the abilities of the ways of learning on the other side. This philosophical German term means a two-sided cultivation between teachers and learners. It is the considerable component of instructional theory and one of the elements which should be taught in the academic area of instructional research on the basis of the students' experiences of actual instruction in primary or secondary schools. It is, however, very difficult for all of the students attending the lecture or the seminar of teachers' college to visit one of the schools and teach the learners in classrooms because it takes too much time for the students to make preparations for their own teaching and it is very difficult to adjust the curricula of primary or secondary schools to those of colleges so that the students can teach the learners in schools and have their practical experiences of "Doppelseitige Erschliessung". So it is neccessary for the students to use an instructional simulation in place of the actual instruction in schools. I made an instructional simulator by means of which they could have their personal simulated experiences of remedial instruction as junior high school teachers who would instruct learners in a calculation of addition and subtraction of plus and minus quantities. Here is used a microcomputer as a simulator for remedial instruction. The instructional simulation is composed of several steps as follows. 1. A student teacher puts some questions on a numerical calculation to learners enrolled in the microcomputer by means of a screen display and a keyboard. 2. The questions are answered by the learners, the model of whose abilities to answer has been programmed in the microcomputer. 3. The student teacher has to select those leaners who make errors in calculation, looking at their answers printed out. 4. He must, then, indicate to the learners in terms of a keyboard what errors they make in calculation. 5. And he must explain in the same way, that is, in terms of a keyboard how they should correct their errors in calculation. 6. The ability level of each learner making errors in calculation will raise if both of the indication and the explanation of the student teacher are suitable. I consider this simulator as one of the teaching aids used in the lecture or the seminar of teachers' college. In future I will make other type of simulator by means of which the students could have their personal simulated experiences of remedial instruction not only in numerical calculation but also in pattern recognition.