This study was intended to find the effect of teaching approaches to the performance of the students in Mathematics. Two teaching approaches which are prevalent in Mathematics are considered: constructive approach and spoon-feeding approach. The Union College School of Integrated Preparatory Studies. Thirty-two out of sixty-five students from the two sections of fourth year high school participated in this study. They were grouped into two (each consisting of 16 students) in such a way that each group equally represents above average and average students. Raised at the beginning of this study were three concerns: the present status of the constructive and spoon-feeding approach as reflected in the teacher-writer, the Mathematical performance of the students after the application of constructive and spoon-feeding approach, and the significant difference between the performance of the group who have undergone constructive approach and the group who have undergone spoon-feeding approach. The concepts regarding the number ?1? were used as topics in eliciting Mathematical performance from the students. These concepts/expressions are the following: a0 = 1 (Exponential Function), 0! = 1 (Factorial) and 0.999? = 1 (Repeating Decimal). First, the students were made to evaluate the teaching approach of the writer using a survey sheet that contains characteristics of teacher using constructive and spoon-feeding approach. Simple mean was used to analyze which of these two approaches is more often used by the teacher. Second, the constructive approach in teaching was applied to the first group to deliver a series of teachings involving number ?1?, while the spoon-feeding approach was applied to the second group, in which, after each teaching session, a short quiz was conducted. The total of the three quizzes was computed for each student. Simple mean was also used to find out the average performance of students who have undergone constructive approach and average performance of students who have undergone spoon-feeding approach. Lastly, the significant difference of the total scores in constructive teaching approach and the total scores in spoon-feeding approach was observed using the t-test for two sample mean. It was found out that the teacher-writer was most of the time using the constructive approach based on the average rate of 4.31 which was given by the students (from the scale of 1-5 with 5 being the highest). The average performance of the students using the constructive approach is 24.44 (equal to 90%) from the total of 30-item quiz, while an average of 17.06 (equal to 78%) for the spoon-feeding approach. The Two Sample Mean Test with .05 level of significance revealed that the tabular value 2.042 is less than the computed value 5.45. Thus, a conclusion that there is a significant difference in the students? performance using the two approaches was considered.