Socioeconomic status (SES) has been shown to be associated with children's arithmetic knowledge as early as kindergarten, which is an important issue, given that early numeracy knowledge and skills usually correlate to later academic achievement in arithmetic. In line with recent research, it is argued that the regular practice of exercises involving cardinality, ordinality and arithmetic transformations during class time could accelerate the progress of children, particularly among low-SES children. Participants were 118 kindergarteners (M[subscript age] = 3.87). Teachers were randomly assigned to the intervention group (immediate implementation of the intervention; N = 64) or the control group (intervention delayed, N = 54). This intervention consisted of playful exercises involving quantities and numerical transformations. The results indicated that the intervention tended to accelerate progress on the verbal numerical sequence, particularly among lower-SES children. In addition, the intervention tended to accelerate progress on cardinality and arithmetic. These results provide preliminary evidence of the effectiveness of the intervention to help children acquire basic mathematical skills.