«We often take an entire grade level of students on field trips at the same time. (educationworld.com)
Even worse, research shows that many classrooms use textbooks written two or more years above the average grade level of their students (Chall & Conard, 1991; Budiansky, 2001). (ascd.org)
where Genderi is a dummy variable equal to 1 if the student is a female and 0 otherwise, and Gradei is a vector of dummy variables indicating the grade level of student i. (educationnext.org)