Why do students make errors is a question that has continued to baffle the teachers of mathematics for a long time. The study reported here was designed to explore the reasons for the lower Secondary School students making particular types of errors. Various possibilities of sources of errors such as insufficient explanations, over generalization of concepts and unorganized board work on teachers' part and faulty reasoning, carelessness and misinterpretation on the part of the students were taken into account. To arrive at a conclusion, students' errors were analyzed and some of the problems teachers encounter while teaching were discussed in detail. This study also investigated the impact of mentoring on the teachers' development specifically to improve the present situation. A substantial part of the dissertation explores my struggle with mentoring the teachers to enable them to understand the philosophy behind the alternative teaching approaches to reduce the errors. The fact that there is a need to guide teachers and administrators to help them organize teaching activities in an effective manner is clearly highlighted.