The College Adjustment Inventory is valid for predicting academic success. Dynamic rather than deterministic universe . Whenever humans are involved, think quantum mechanics rather than simple cause and effect. Humans are probably better likened to the chaotic world of subatomic particles than to the neat world of Newtonian physics. People seldom behave as predictably as billiard balls.
Humans exhibit tendencies rather than inevitabilities.
There are many factors which contribute to an individual's behavior. We will never know all of them. Smarter people tend to make better grades, but not always. Ambitious students tend to make better grades, but not always. The less gifted student can improve performance by working harder and getting help.