This study aimed to raise the achievement level of students in Differential Calculus using Direct Instruction with Salazar’s Grouping Method in a flipped classroom and Small Group Method. The quasi-experimental method of research was used. The study also employed qualitative and quantitative analysis relative to data generated by the Achievement Test and Math journal with follow-up interview. Within the framework of the limitations of the study, both methods of grouping revealed a significant increase on the gain scores within each group but no significant difference was obtained between groups (control and experimental). However, a slight difference of mean gain scores in the Achievement Test was revealed in favor to the experimental group. Moreover, qualitative assessments showed that both grouping methods develops self-confidence, encourages effective communication and facilitates exchange of ideas towards a common goal. The students from both groups were in favor with the sequence of the presentation of the lesson, especially with the incentives given.