The most significant effect of absences on students' grades is loss of credit. All schools have a maximum number of unexcused absences for a course or school year. Check with the school district's handbook to find out the total amount of absences allowed before credit is taken away. Normally, students can miss no more than around 20 absences. If a student exceeds this amount without submitting documentation to excuse them, he loses credit. Even if a student has an "A" in the course, the grade is changed to an "F" if he is in credit withdrawal.
When a student misses school for even one day, he is given make-up work upon his return. In high school, for example, a student is enrolled in five to six academic subjects. In each class, the homework alone can take a student a full hour per course. Having to double that amount of coursework can be overwhelming. A student can lose points quickly if he cannot complete make-up assignments.
Sometimes excused absences can affect students' grades more than unexcused ones. Students who play sports or participate in clubs often miss multiple classes for field trips or games.The student is responsible for all missed work, but has not received the instruction necessary to complete it. A student athlete, for example, can miss 20 days of a last period class for games in a single marking period. In subjects such as math and science, where direct instruction can be essential, students can find themselves failing, simply because they chose to play sports.
When students miss school for an extended period of time, their grades normally suffer. Students who are chronically ill, or who get a sickness that requires them to miss a week of school, miss so much during that period of time it is difficult to recover academically. A student returns and must try to make-up work for multiple classes. Some teachers fail to consider the amount of work a student is asked to make-up for each class and make unreasonable demands about when it needs to be completed. As a result, even the strongest student's grade can plummet quickly when multiple days are missed consecutively.