Many teachers experience difficulties in starting an instruction and in how to make the students learn appropriately. Meanwhile, the teacher has to make the students learn in order the teaching conforms to the four pillars of education according to UNESCO, i.e.: learning to know, learning to do, learning to be, and learning to live together in peace and harmony. In relation to this, a study was conducted to the students of primary schools in Singaraja to see the effectiveness of BLCS model (Bruner, Local Culture, and Scaffolding) in the teaching of mathematics through a measurement using Expert System - based CSE-UCLA. The effectiveness of the teaching model was seen from learning activities, learning achievement, and the students' response to the teaching. Data were collected through observation, test and questionnaire and were then analyzed descriptively. The results show that BLCS model is an effective model to be used in the teaching of mathematics.