This paper presents the comparison between English writing skills on narrative and persuasive writing of students of Secondary School Certificate (SSC) and Ordinary level (O level). In this quantitative study, we selected private schools of Lahore that offered both streams simultaneously. We developed the Essay type test with the help of English teachers of secondary level to assess students' learning outcomes at SSC and O level. Similarly, rubrics were developed for scoring students' responses to writing test. We assessed writing learning outcomes cumulatively and by dimensions, such as developing and organizing ideas as well as mechanical accuracy. Results showed that learning outcomes, overall and separately for narrative and persuasive English writing were higher at O level as compared to SSC, indicating that O level students acquired better writing skills than SSC students. Within each narrative and persuasive writing, by dimensions learning outcomes were found higher at the O level than the SSC. The findings of present research are anticipated to upgrade the quality of assessment that may lead to quality teaching in English writing classrooms. Moreover, this could also help in improving assessment strategies in English writing classes at secondary school level and may pave the way to help teachers towards successful attainment of the desired learning outcomes. For future research, motivation of students towards learning may play an important role in improving the writing learning outcomes.