In prisons, security, infrastructure and restricted Internet access have considerably hampered the deployment of educational technology. This paper compares the effectiveness of offline Study Desk (OSD) teaching plan an offline online learning method working without any internet connection in enhancing achievement in Physics among inmates in the popular correctional facilities in Kenya. Quasi-experimental design was used to test the hypothesis; pre-test and post-test measurements were obtained on two sets of inmates being taught using OSD and lectures respectively. Descriptive and inferential statistics were used to test the quantitative achievement and quality of OSD delivered learning was analyzed using descriptive statistics. The findings revealed OSD's impact on engagement and self-regulated learning and examination scores. Policy implications and suggestions for the use of offline safe online learning environments in correctional facilities education in Kenya and beyond is discussed in the paper.