Too few mathematics teachers have the expertise to apply baseline assessment for differentiated learning in mathematics classes. This empirical study was conducted in a focus group of sixty learners and three teachers in a grade four mathematics class. It proved that teachers of mathematics in elementary grades could profitably learn to conduct baseline assessments; developing activities to benchmark learners' abilities and learning needs. The exploratory research design was utilized to set up the general sample and the focus group, and mixed research methods; qualitative and quantitative instruments to collect data and analyzing data. The records of scores obtained by learners from the assessment activities and the interviews with teachers were the main sources of data. Data analysis followed quantitative procedures and presented in figures and categorized them in frequency distribution tables. Findings highlighted that learners can reach their optimal levels in learning mathematics in a free and flexible environment. This paper concludes that the lack of knowledge about how to conduct baseline and its value is one of the attributes of the high failure rate of children in the middle class. This article recommends the consideration of baseline assessment to be an essential aspect of a continuous professional development program for mathematics teachers.