- Socioeconomic status: Students from families with higher socioeconomic status may have better access to nutritious food, including breakfast, and may also have more resources and support for academic success.
- Family environment: Students who live in stable and supportive family environments may be more likely to eat breakfast and have better overall health and well-being, which can contribute to academic success.
- Peer influence: Students who have friends who eat breakfast may be more likely to adopt the habit themselves.
- School environment: Schools that provide breakfast programs or have a positive school climate may encourage students to eat breakfast and support academic achievement.
- Individual differences: Some students may have individual preferences or medical conditions that affect their ability or desire to eat breakfast.
Without controlling for these and other hidden variables, it is difficult to determine whether the relationship between eating breakfast and higher grades is causal or due to other factors.