GPA prediction of college student
Perhaps you can see if Graduated_high_school is correlated in any way to GPA_college? If there is no correlation, you can try to fit a model by dropping the Graduated_high_school column.
Else, you can try to drop rows belonging to under-represented high schools. However, one problem I foresee is that future predictions might have Graduated_high_school that are unseen in the training dataset, leading to problems (e.g. schools that weren't mentioned in the dataset, or if someone  decides to use your model, on a dataset from another country). So, if the Graduated_high_school is not important, I would consider dropping it altogether.
Or, maybe you can change Graduated_high_school to something else that is related, such as number of teachers in high school, teacher-student ratio etc.