This study was conducted to determine whether Ontario students' abilities to apply rubrics accurately in order to self-assess or to assess peers' written work were related to their current levels of achievement in writing. The project examined differences in assessment ability for children attending different grades, gender differences, differences between Anglophone and Francophone students, and differences among students identified as learning disabled, talented, and gifted. Statistical analyses were performed on the combined data collected from participants in grades 5 through 8 in Anglophone and Francophone Ottawa area schools from the pilot project, with 144 students sampled in 2000 and 626 sampled in 2001. These analyses explored the relationship between the variables of writing level in school and the accuracy and severity with which the students applied the Ministry developed rubrics for their grade level of writing, as well as the confidence students felt when assigning rubric levels to others' writing samples. Significant differences in these variables among groups were also explored. A significant relationship was found between writing ability and accuracy in applying the rubrics for assessment of exemplars. School grade also had an impact on how well students apply the rubric to exemplars. Students in grade 6 were significantly more accurate than students in grades 5 or 7. Differences in ability to apply the rubrics accurately between the reference group and learning disabled and gifted are reported, as well as differences in confidence levels for these groups. Girls identified rubric levels more accurately than boys, but this may be an artifact of their general increased proficiency in writing, a finding that would strengthen the general finding of a relationship between ability in writing and the ability to apply the rubric accurately. (Author/SLD)