The onset of COVID-19 forced restructuring of the teaching-learning system from replacement of offline education to online education -- to ensure continuation of learning. Sudden transition in the education mode is bound to affect students' learning progress and may lead to learning loss. Under a circumstance of lack of empirical evidence, the present study renders some empirical insights on the factors leading to learning loss of students from different educational levels. For this purpose, 228 students from each educational level of institution -- school, colleges and university -- have been selected by applying a stratified random sampling technique. We apply ordered logistic regression to investigate the factors affecting the success of the online teaching-learning system and compare the same along different parameters like location and ownership of the institution, and gender of the students. The findings indicate that inadequacy of digital infrastructure and the socio-economic and demographic characteristics of students contribute to high levels of learning loss. Further, the location of the educational institute adds to discrepancies in learning progress. The study suggests the requirement of providing necessary support to remove the digital divide and ensure equitable access to learning platforms at all educational levels.