NEW YORK ( TheStreet) -- If your son or daughter is bringing home mediocre grades from college, go ahead and grouse all you want. But in the end, you're as responsible for those C, D and F grades as your child. How so? As usual, it's all about the money. A University of California, Merced, report ties study habit and grades to the financial help students get from their parents. Author Laura T. Hamilton, a sociology professor from the school, says the more money junior gets from mom and pop, the less they are likely to flourish academically or earn stellar grades. Hamilton's study, More is More or More is Less? Parental Financial Investments during College, says significant parental financial support won't result in a student not graduating, but it will weaken their academic performance. "Students with parental support are best described as staying out of serious academic trouble, but dialing down their academic efforts," Hamilton says. The terrain has definitely shifted on the college financial front, she adds. Skyrocketing tuition costs are taking a toll on students and families. According to the College Board, the average published tuition and fees for in‐state students at public four‐year colleges and universities increased from $8,256 in the 2011‐12 academic year to $8,655 now. Colleges say their hand is forced, with weaker external funding causing them to raise tuition costs. That has also forced parents to step up and shoulder a bigger burden. But Hamilton says that college students spend, on average, 28 hours per week on classes and study -- fewer hours than the average high school student. What are collegians doing the rest of the week? They're spending 41 hours on social and recreational events, the university reports. It may be better if the kids feel they have "earned" college financing. Hamilton's data show that money from grants, scholarships, work study programs and other nonparental benefits do not hurt students' grades -- instead, students who get such benefits believe they earned them, as opposed to having the cash handed them by parents. "With decreased state and federal support for higher education, however, outside funds are increasingly hard for families to access," Hamilton says. The good news: Students who get more financial help from mom and dad are more likely to graduate, Hamilton says. Her data show that students with zero financial help from their parents during the first year of college had a 56% estimated graduation rate, compared with 65% for collegians who got at least $12,000 from their parents. Hamilton is certainly not calling for parents to stop paying for their kids' college costs. What they can do is set standards for grade point averages and make them accountable for their academic performance. Sounds like a fair deal, right? Bring home A and B grades and keep the parental gravy train rolling. If that means college students are just going to have to hit fewer parties to get those higher grades, so be it.