The first grade is the cornerstone of the student's education in school. Achievements at this grade wield huge influence on a child's interest and development of a positive attitude towards education and learning environment. The purpose of this study is to investigate the academic factors of first grade retention in primary schools in North Khorasan. In the first study, a causal-comparative method and in the second study, a qualitative method are adopted. The statistical population includes all first-grade students, their teachers, and parents in North Khorasan province. The first study' sample consists of 351 students who were divided into three groups of grade retention, weak academic achievement, and strong academic achievement. The second study consisted of 30 first-grade teachers. Data collection tools included Parental Involvement in the Child's Education Scale, Student-Teacher Relationship Scale, Researcher-Made Questionnaire, and semi-structured interview. The results showed that the parents of students with grade retention and poor academic achievement had limited participation in school activities. Teachers also had more conflicting relationships with weak students that were retained. According to the results of the qualitative method, three components of attitude, cognition, and behaviour in the teaching process served as qualitative subcomponents of difference between teachers of retained students and teachers whose students were not retained. The results have many implications for the prevention and reduction of grade retention, especially in the first grade.