Curriculum-Based Measurement (CBM) has many effective uses in the school system and its use is increasing. Most CBM research focuses on the area of reading and little on writing. Only one study was found that examined the effects of choice in story starters on students’ writing performance, and a few studies examined the effects of interest level of writing topics, although none using CBM as a measure. Past research has indicated girls score significantly higher on CBM measures of writing than boys. This study investigated if choice and interest level in a story starter topic have an effect on students’ writing performance. This study investigated the differences between third grade boys and girls on two different CBM-Written Expression probes using production-dependent, productionindependent, and accuracy scores. The results indicate that when no choice is given, girls do score higher than boys. However, when given a choice of story starter topics, boys’ performance on the CBM measures is comparable to girls’ performance. Furthermore, higher interest in story starter topics lead to higher scores as well.