Bedtime is fight time at my house. I know my daughter is happier, more cooperative and easy going when she gets enough sleep. She likes to avoid going to bed, dragging her feet and stalling in lots of creative ways. When I'm tired it drives me nuts. "Cause I said so," never flies that well and logic rarely works either. But the next time bedtime turns into a main event I have a new card to play – science.

A new study by Yvonne Kelly, an epidemiology and health professor at the University College, London, found evidence that a regular bedtime boosts a child's IQ.

"Not having a regular bedtime in early childhood is linked to various aspects of intellectual development - here we looked at reading, math, and spatial abilities," says Kelly. "We found that children [without regular bed times] had lower scores compared with children who had regular bedtimes." There's lots of evidence showing a link between inconsistent sleep habits and poor academic performance in adults and teenagers, but this was one of the first to look at the link in children. Kelly and a team of researchers used the Millennium Cohort Study, a collection of information gathered from 11,178 British children born between September 2000 and January 2002.

Kids who are tired are at a disadvantage at school - read our Goonight, Sleep Right piece to learn how to set a bedtime.

Part of the cohort study involved four interviews with kids and parents – at nine months, three years, five years and seven years of age. Interviewers asked about bedtime routines, how often the kids went to bed "on time" and whether they were read to or watched TV before bed. During the later three interviews the kids were also given a standardized IQ test involving reading, math and spatial-awareness.

Even when variables like bedtime reading, bedroom televisions and family socioeconomic status were controlled, Kelly's study showed a regular bedtime effected IQ scores. But the effect was not equal. Girls with regular bedtimes scored an average of eight points better than those without. Boys too felt the impact of bedtime routines, at least when they were younger, scoring six points better on the IQ test at age three if they had regular bedtime, but the difference disappeared by the time they were seven.

If you're looking for books for nighttime reading, look no further than our gallery of Top 10 childhood books that are still around.

Kelly cautions not to make too much of the gender divide. "I don't think we can draw any firm gender related conclusions from this work," she said. "The differences we found were not statistically different. They don't, for example, suggest that somehow girls are more prone and boys immune to the effects of not having regular bedtimes."

That's a sentiment shared by Alanna McGinn, a sleep consultant at goodnightsleepsite.com. She says all kids benefit from a regular bedtime (and she's got plenty of testimonials from parents saying they benefit, too). The bedtimes she recommends to her clients vary by age: 15 months to three years, 6 to 7:30; three to six, 6 to 8; seven to 12, 7:30 to 9.

"[Children] thrive off of consistency and having a regular bedtime helps them to know what is coming next," McGinn says. "As much as [children] pull for control they actually feel more safe and secure when parents are in control. When things are irregular that's when the struggle can occur because they're unsure of their next step." Further, she says, regular bedtimes help set the natural internal clock, which optimizes restorative sleep patterns.

So, now I have more ammunition for arguing for a regular bedtime, but that doesn't mean it will get any easier. For that McGinn offers five tips. These can work for adults struggling to fall asleep, too. Communicate. "Discuss the importance of sleep with your child," she says. "It helps them understand why its important and why you are making the necessary changes to their routines." Ask them why they need sleep, how much sleep they think they need, how they feel when they are tired and how they feel when they get a good night of sleep. Avoid caffeine and sugar. Just like in adults they are a stimulant that makes falling asleep harder and have many other proven health issues, especially for kids. Avoid caffeine throughout the day and soda, chocolate and iced tea from late afternoon on. Encourage quiet play. An hour before bedtime, turn off the TV and computer. "Electronics right before bedtime can put the body in a state of stress because of the high level of visual and cognitive stimulation," says McGinn. Try a game of cards, a puzzle or imaginary play with toys. Establish a routine. Creating a consistent sequence of pre-bedtime activities "sends cues to your child, consciously and unconsciously, that it's almost time for bed," she says. Warn them that it's almost bedtime. Then, 15 to 30 minutes before bedtime, McGinn recommends dimming the lights to trigger the natural release of sleep hormones, playing soothing and quiet music, brushing teeth and reading. Consistency is key. Have your child go to bed and wake up at the same time every day,

McGinn recommends. "Even on weekends, you shouldn’t stray more than an hour or so from bedtime in order to continue to synch their circadian rhythms and their brain." 

Adults have trouble falling asleep too. Here  is a Bedtime yoga routine you can try, plus 10 secrets to a good night's sleep.