School tutoring and academic performance: A too close relationship?

•In Spain, each student class is assigned a tutor teacher.•We employ rich administrative census data from the most populated region of Spain.•We employ student fixed-effects within-students between-school subjects.•Tutors seem to be inclined to slightly over-mark their tutoring students.•Over-marking may be unconscious and based on tutors’ relationship with the student. In Spain, each student class is assigned a tutor teacher who is also responsible for individually following their tutoring students’ performance, guiding them in personal issues and regularly meeting their families. Although tutors may suppose an important support for students during their school life, their close personal relationship may also influence the teaching and learning process in additional ways. This research analyses whether the fact that the tutor teaches a particular subject makes any difference in students’ academic achievement in that subject and if this differential achievement is conditioned by tutor-student/family relationship or not (being a possible over/under-marking). With this objective we employ a rich administrative census database from the most populated region of Spain (Andalusia), using student fixed-effects within-students between-school subjects. Our main results show that tutors seem to be only slightly inclined to over-mark their tutoring students, being this small bias conditioned by their relationship with the student.