Here is an excellent parent resource and Graphic from Living Sky School Division, Saskatchewan illustrating how by Grade 3, 79% of students with absenteeism of only 2 days per month can do Math at grade level versus 88% of good attenders who can do Math at Grade 3 level.
Failing grades in Math is an early indicator by Grade 6 of early school leavers or drop outs in Destination Graduation: Sixth Grade Early Warning Indicators for Baltimore City Schools – Their Prevalence and Impact.