Truancy, chronic absenteeism, and average daily attendance are three different measures used to describe student attendance in schools.

Truancy refers to a student's unexcused absence from school without the permission of their parents or guardians. Typically, a student is considered truant if they miss a certain number of days of school without a valid excuse, which is set by state or local law. Truancy is often seen as a problem behavior and can lead to disciplinary action.

Chronic absenteeism, on the other hand, refers to a student's absence from school for any reason, whether it is excused or unexcused. In general, a student is considered chronically absent if they miss 10% or more of the school year. Chronic absenteeism is a more inclusive measure than truancy because it takes into account all absences, not just unexcused ones, and recognizes that even excused absences can have a negative impact on a student's academic progress.

Average daily attendance (ADA) is a calculation of the total number of students present on each day of the school year, divided by the total number of days in the school year. ADA is often used as a measure of school funding because it reflects how many students are actually in attendance each day. Schools with high ADA may receive more funding than those with low ADA because they are perceived as serving more students.

In summary, truancy refers to unexcused absences, chronic absenteeism includes both excused and unexcused absences, and average daily attendance is a measure of the total number of students present each day of the school year.