The decimal in the grade level can be thought of as the number of months. For example, 5.8 can be interpreted as the 5th grade level and 8 months.

However, no student has complete knowledge of all preceding topics, so it would be incorrect to assume a student whose grade level is 5.8 knows all topics covered in the 4th grade. The grade level is an easy metric to compare students, but to understand exactly what the grade level represents for any student, you should review all the grade proficiencies and missing skills of that student.

The grade level score is calculated from each of the grade proficiencies, and each grade proficiency is the the percent of standards known per grade level.  For example, a student that knows 80% of the kindergarten standards will have an 80% grade proficiency for kindergarten. Passing 80% of the standards in a grade level is equivalent to being 8 months into that grade level. If this student also knows 50% of the grade 1 standards, the overall grade level is 1.3 (80% + 50%).