Why Your Teen Needs a "B" Average

(MoneyWatch)  Wonder if your teenager is going to perform well in college?

The most powerful predictor of a student's college success is his or her high school grade point average.

The magic GPA seems to be 3.0. Teenagers who earn at least a 3.0 GPA are far more likely to graduate from college than their high school classmates who eke out a 2.9 GPA or lower.

That's one of the many fascinating findings of a new book, Crossing the Finish Line: Completing College at America's Public Universities, which was written by three academics including William G. Bowen, Princeton's former president. In measuring the academic success of college students, Bowen and his co-authors plowed more than 200,000 educational records of students who attended flagship and public universities across the country.

Plenty of other studies have also concluded that students' grades and not SAT or ACT scores are the most critical predictor of college success, but I was intrigued by the evidence that supports the power of the "B" average.

Here's a fascinating example that I pulled from the book that illustrates why high school students should strive for at least a 3.0 GPA:

The researchers discovered a significant gap in graduation rates among students with a "B" average and those who only fared slightly worse. Students with a 3.0 GPA had a 51% chance of earning a bachelor's degree, but students with a 2.99 GPA faced only a 39% chance.

Not surprisingly, "A-minus" students graduated at a higher rate than their "B" classmates, but their success rate didn't increase as appreciably. A student with a 3.33 GPA enjoyed a 57% chance of graduating from college. (To give you perspective on graduation odds, 40% of college students never earn a bachelor's degree.)

Here's another finding that astounded me: Regardless of whether "B" students did poorly on the SAT or aced the standardized test, their chances of graduating from college were almost identical. Forty nine percent of "B" students who performed poorly on the SAT (800-890 score out of possible 1600) graduated in six years versus 51% for the superior test takers who scored 1100 or above. That's barely any difference in graduation rates.

Curiously enough, the researchers concluded that it doesn't matter where a student earns a B average. The academics speculated that what is crucial is that students apply themselves regardless of whether they attend a rigorous private prep school or an inner city school that's plagued with an alarming drop-out rate. If a student can be focused, organized and studious in high school, they are likely to carry their academic habits with them when they start college.

So what does this mean? Next time you are tempted to nag your son or daughter to study for the SAT or ACT, maybe you should just tell them to do their homework instead.

Report card image by samanthaschnurr. CC 2.0.