Since Singapore became an independent republic, careful language-in-education planning that caters to the economic, social, and political development of the country has never been abated. A notable case in point is the constant reviews and reforms of the curriculum of Chinese language (CL), a school subject required of ethnic Chinese children, to respond to gradual home language shift from CL toward English, which is the medium of instruction, in the country. In 2008, a differentiated Modular Curriculum (MC) began to be implemented in all primary schools. We were subsequently commissioned by the Ministry of Education to evaluate the MC. We analyzed CL teaching materials, observed and coded CL classes, and engaged students and CL teachers through various methods. In this chapter, based on student surveys as well as a teacher survey and focus group discussions, we report some evaluation findings on how students' interest in CL learning and use changed, how the MC and its underlying principles were perceived by teachers, and what difficulties and challenges teachers experienced under the MC. Based on the findings, we discuss the interface between sociolinguistics, curriculum innovation and reform, and language policy and planning; and underscore boundary crossing in curriculum and program evaluation toward evidence-based language-in-education planning. [For the complete volume, "Crossing Boundaries in Researching, Understanding, and Improving Language Education: Essays in Honor of G. Richard Tucker. Educational Linguistics. Volume 58," see ED672546.]