Scoring mathematics exam papers accurately is vital for fostering students' engagement and interest in the subject. Incorrect scoring practices can erode motivation and lead to the development of false self-confidence. Therefore, the implementation of appropriate scoring methods is essential for the success of mathematics education. This study aims to explore scoring variations among teachers and improve their performance in this crucial aspect. Participants in the study comprised 65 high school mathematics teachers (31 male and 34 female) who evaluated an exam paper during an initial session of an in-service program. After a three-month interval, the teachers reassessed the same exam paper. The results analysed using one sample t-test, paired samples t-test, and one-way ANOVA, reveal a significant improvement in teachers' scoring performance. These findings underscore the significance of ongoing professional development to enhance teachers' scoring accuracy and consistency, particularly for less experienced educators, ultimately benefiting students' mathematics education.