It's the big question for parents School now? Or later?

More parents are holding kids back a year... while others start early.

So what's the right choice, and how do parents know for sure?

Four-year-old Joshua Payne is content playing on his computer at home. But his mom Kristine worries that won't be the case for long. He's in preschool now, but she feels he's ready for more.

"It's good for Josh because of the fact he has ADHD. He's constantly needing to be challenged," says Kristine.

The problem is, Josh's birthday is September 27...four weeks after the state's September 1 cut-off date.

But if he has to wait until next year...Kristine worries he'll be a disturbance to the rest of the class.

"Because of the fact he's gonna know everything they're doing, and he's gonna be bored with it."

University of Wisconsin Education Professor Beth Graue says that's possible. She's spent more than a decade researching kindergarten preparedness.

"There is a small advantage for kids to be slightly older, but it's a short-term advantage...Results have found that children older than their peer group are more likely to have social and emotional problems."

Katie Dahm says that's not the case for her son Will. She held him back a year... and says he's doing very well in kindergarten now.

"I feel we rush our kids so much now...We're not allowing them to be kids," says Katie. "He just needed an extra year to mature. Grow up and become a little more socially mature."

But it's not just a social issue...It's also academic. Kids are expected to know more, sooner.

According to state law, if parents want to start their child early, that child must be tested.

Pewaukee Elementary School Principal Deb Ristow explains, every school district has its own test. She explains their procedure.

"An IQ test by the school psychologist, and probably an interview with the parents on the social/emotional development of the children."

But Ristow says, while the schools have rules they must follow, parents know best.

"They are their child's first and most important teacher. Kids are so different, and their environments growing up are so different, it's really hard to predict."

Katie Dahm says holding Will back was one of the best decisions she's ever made. She says, she'll never forget something a nursery school director once told her.

"She said to me, Katie, I've never met someone who's regretted holding their child back, but I've met many people who've regretted not holding their child back."

Meanwhile, Kristine had Joshua tested for early entry in the Cedar Grove School District. He did not meet the passing requirements.

"I don't think it's fair at all. I think it's ridiculous. I think he should be given the chance," says Kristine.

Kristine says she plans to fight the system, and possibly home-school Josh if she has to.

Another issue to consider is the consequences of varying ages in the classroom. For example, you might have a kindergarten class containing 4, 5, 6, even 7-year-olds. That makes for a big size difference, and differing maturity levels.

Graue's studies also show that girls who start school early tend to thrive in the long run.

Parents are more likely to hold a boy back a year.