One important point is auxiliary problems that affect schoolwork but don't relate directly to schoolwork as attitude and a sense of discipline might be said to relate directly to schoolwork. These auxiliary problems include health and relationship problems. Looking at health first, many students have chronic or as yet undiagnosed health problems that prohibit them from completing schoolwork.
While it is hard to believe in our contemporary age, many a student has undiagnosed or unmanaged chronic illnesses like hypoglycemia or asthma or chemical sensitivity that will interfere with their performance. For instance, undiagnosed or unmanaged asthma may cause memory to be impaired, which would impact both ends of homework, remembering to take it home and remembering what it is for once it gets there!
There is much brought to light about the sorts of relationship problems a student might typically suffer at home--parents fighting, etc.--but there may also be abusive siblings or neighborhood bullies. All of these things will impact a student's ability to perform schoolwork. And on the college level, as I know trophyhunter teaches at the college level, illness can still be a major factor that is worsened by being compounded by things like imprudent lifestyle or growing complications to the existing illness, like a roommate or floor-mate who drowns themselves in synthetically manufactured fragrance (do use essential oil fragrances like Yakshi Fragrances or Purple People Oil Emporium). Relationships also get complicated with some parents announcing the actualization of delayed divorces or with broken hearts from first serious romances.
So while a student's character and habits may be the cause of neglected homework or college studies, serious difficulties may also be the cause. I'm personally all for checking for serious problems first. In addition, at the college level, some students, like actor Jason Bateman, just want to go "wild" after being "good" for what seems like "so long."