The COVID-19 pandemic caused some serious setbacks in primary and secondary education wordlwide. In 2021, the Estonian Ministry of Education and Research (MoER) contracted a group of researchers and expert teachers to design and validate of a set of innovative digital learning resources that support personalized learning paths to meet the needs of a diverse learners trying to work on their knowledge gaps caused by pandemic. This paper presents the results of designing a set of innovative open educational resources for 9th grade mathematics and piloting these in nine pilot schools. Based on the analysis of the results, we identified the main technological and pedagogical challenges in supporting flexible learning paths with interactive digital learning resources in post-COVID mathematics education.