ONE OF the great mysteries of all time - alongside Stonehenge and tomato plant wilt - is what motivates a teen-ager to succeed in school.
If parents knew the answer, fewer teen-agers would have to wait until the next report card before getting their driver's license, and more would go on to college.
By the time a teen-ager enters high school, academic habits are usually well-established and - with their kids grown so big and mouthy - parents are either counting their blessings or throwing up their hands in resignation.
Unfortunately, science hasn't been much more successful in discovering what motivates teens in the classroom.
But a study team at Child Trends, a nonprofit, nonpartisan research organization in Washington that studies children, youth and families, has combed through the research out there and drawn a few solid conclusions about what works.
And the research analysts can also say with some authority what we don't yet know.
"The quality of the data is very mixed," said Kristin Moore, president and senior scholar at Child Trends.
"The study team ended up throwing out a lot of very poor research.
"We can't say much about vouchers, school choice or uniforms or a lot of the hot educational reform topics out there.
"But there is quite a bit of information on parental involvement."
For something that is so clearly an indicator for academic success, high school graduation and continued education, "parental involvement" certainly has an amorphous feel to it. But Child Trends senior research analyst Jennifer Brooks defined it this way:
"It is about creating a culture in the family around school, around the importance of education," she said.
That can be as simple as insisting your child attend school every day or as contentious as insisting he turn in homework that is complete and shows effort.
It can be as simple as showing up at back-to-school night and parent-teacher conferences and as challenging as steering her into extracurricular activities where she will have positive experiences and meet kids who demonstrate the academic motivation you want for her.
"There are probably other things that matter," said Moore. "But these are things we can show."
Some other findings:
The amount of TV a teen watches appears to have less impact on their academic achievement than the number of hours they work at a job.
It is not clear exactly why, but more than 20 hours of work a week appears to "disconnect" a teen from his school, and it does not bode well for good grades, graduation or college.
Tracking matters, too. Academic achievement seems to be contagious among teens who are in college-track courses or in higher-level courses - whether their previous school record shows such promise or not.
Mentoring or tutoring programs work, too. These include Big Brother/Big Sister or Boys and Girls Clubs.
Parents often believe that their teens are so peer-centric that they aren't heard even when they are shouting out loud.
But according to Moore, the research into peer relationships is as clear as mud.
"The problem is, it is difficult to know if they choose certain friends who are also not doing well, or if they are not doing well because of the influence of their friends."
Certainly peers influence our teens positively or negatively, but the research doesn't show which direction the current is flowing.
But the impact of parents is very clearly demonstrated in the mountains of research through which research analyst Zakia Redd and Brooks combed.
"The style of parenting is important," says Brooks. "Parents who are authoritative - accepting and involved, but also strict and a source of consistent discipline. These teens do better."
"One of the clearest indicators and predictors of success is parental involvement," says Redd. "That is the main take-home point.
"When parents communicate with their children about their expectations and about the importance of education, the kids seem to do better in school and go further educationally."
Child Trends has done the spade work to demonstrate something beleaguered parents have come to doubt.
Our kids are listening to what we say about the importance of school whether they appear to be or not.
We just have to keep on talking.