While existing research has well-recognized educational plan as an important predictor of students’ educational achievement, the alignment of educational plan and achievement should not be taken for granted. As plan-achievement misalignment is liable to negative psychological and social consequences, this study aims to examine the extent to which parents vis-à-vis teachers could guide students into plan-achievement alignment. Specifically, this study is set within two comparable cases of Taiwan and Hong Kong to explore whether the relative importance of parents’ and teachers’ guidance would differ according to the institutional contexts of education systems. Methodologically, society-specific (multinomial) logistic regression analyses are conducted based on the data of the Taiwan Education Panel Survey and the Hong Kong Survey on High School Students’ Aspirations for Higher Education and Employment. In Taiwan, we find students not only received more guidance from parents, but parents’ guidance was also more effective in helping them reach plan-achievement alignment. By contrast, teachers are found to have played a key role in these regards in Hong Kong. The findings provide support to our propositions that the relative importance of parents’ and teachers’ guidance may vary by the opportunity structures of post-secondary education and the level of school-based parental involvement. Copyright © 2021 National Institute of Education, Singapore.