Deaf and hard of hearing (DHH) students in Hong Kong face great challenges in academic learning since for decades oral language has been the only means of communication in classrooms. The establishment of the Sign Bilingualism and Co-enrollment in Deaf Education (SLCO) Program aims to provide an accessible mainstream environment that supports DHH children's education. This study explores the impact of SLCO education on DHH children's academic performance. A longitudinal study was conducted for four cohorts of DHH students (n = 24) who completed their 6-year primary education at the SLCO school. Data on their academic performance based on standardised assessments in Chinese Language, English Language and Mathematics were collected over the six years of primary education to review their development against normative grade levels and annual growth rates. Results indicate that SLCO-DHH students achieve normative standards in both English Language and Mathematics based on their median grade levels. They do, however, lag behind normative standards by one year in Chinese Language. When their academic development was analysed annually, they were comparable to their hearing peers, with an average growth rate very close to "1" for all three subjects. Additionally, no significant relationships could be found between degrees of hearing loss and speech perception and their academic performance. Instead, early Chinese literacy attainment serves as a strong factor predicting their later academic attainment in both Chinese Language and Mathematics. The SLCO education environment appears to be an education model that effectively reduces barriers to accessing academic content in classrooms and promotes positive academic development.