Psychologists have a bunch of methods for parents to try to get their kids to sleep. They have terms like "unmodified extinction", aka crying it out, which means leaving the kid in bed until morning, no matter how much crying or complaining goes on. "Graduated extinction" means the parent weans the kid from being around others by putting him or her to bed still awake, and slowly shifting the amount of time the parent waits with the child to shorter and shorter periods.
Another time-related trick is "bedtime fading" which calls for the
slow rolling back of bedtimes of children who prefer to go to bed
late. Sometimes psychologists also advocate counseling for problem
sleepers and suggest the children and their parents construct a plan
together to achieve a targeted bedtime. This makes it into a project
for the kid. Good sleep
hygiene is recommended for children, as it is for everyone. Kids
can especially benefit from a set bedtime routine before they go to
sleep, perhaps involving story reading, a bath, or changing into pajamas.
This helps reinforce the child’s circadian clock.
Children sometimes suffer from sleep-onset association disorder.
How much "should" kids sleep? The consensus answer is: more! Insufficient sleep causes poor academic performance, as many teachers know. Commenters have bemoaned the lack of a defiitive answer from science and noted that for decades and even centuries pundits have been recommending longer sleep times. However, a large study published in 2012 found that American kids in early childhood through early adolescence generally did get enough sleep.
A recent Swiss study found shorter sleep durations on weekends were associated with higher IQs. The researchers hypothesized that the higher IQ kids had better sleep efficiencies.