As a former middle school teacher, I can recall countless instances in which students would begin to nod off during class. Their eyes would start to glaze over, their heads would begin to nod, and in many cases they would soon be sound asleep at their desks.

In conversations with these students, many would tell me that they had not gotten enough sleep the night before for a variety of reasons. Watching a late-night program, staying up to finish homework after extracurricular activities, getting home late from visiting family or friends, noisy households or simply not being able to fall asleep were some of the more common reasons for drowsiness I heard over the years.

While it was normal for any of my students to show up for school sleepy once in a while, I noticed over time that the chronically sleepy students were often the same students who received poor grades or had consistent difficulty paying attention in class.

Research has suggested that there is a link between lack of sleep and poor school performance in children. Howard Taras, M.D., acting chief of Community Pediatrics at the University of California, San Diego School of Medicine, was recently commissioned by the National Coordinating Committee on School Health to review hundreds of research studies that looked at the relationship between school performance and various health concerns.

“Of all the health problems investigated, poor sleep was among the most unexpected and definitive causes of poor academic achievement,” Taras said. “Most children need at least nine hours of restful sleep each night. However, for many reasons, school-aged children and adolescents may receive less than the recommended amount. There is evidence that this affects school performance.”

Obviously, a student who is sound asleep during classes will not be capable of adequate school performance. But even sleepy students who are able to stay awake in school may not be able to fully grasp and understand the class material. According to the Mayo Clinic, a sleep-deprived child may have trouble with concentration, memory, physical performance and decision-making in school.

The National Sleep Foundation (NSF) found that more than half of all adolescents report feeling sleepy during the school day, and children who get less than eight hours of sleep per night are more likely to get lower grades than their peers who get optimal sleep.

Along with the potential for poor academic performance, behavioral problems can also result from a student’s lack of sleep. In my experience as a teacher, students who were excessively sleepy were more prone to be uncooperative and irritable, which sometimes also led to problems with other students.

The Mayo Clinic notes that children who do not get enough sleep can be either grumpy and lethargic, or tend toward the other extreme and become hyperactive. These children may also exhibit a short attention span, irritability or restlessness, low energy and activity levels, and be more tearful, anxious, defensive or impatient than usual.

“Irregular sleep patterns negatively affect students’ biological clocks and sleep quality — which in turn affects their ability to perform well in school and their moods,” said Mary Carskadon, Ph.D., director of the E.P. Bradley Hospital Sleep and Chronobiology Research Lab at Brown University.

A lack of sleep in school-age children can sometimes be caused by changes in their lifestyles. A busy schedule, including involvement in extracurricular and social activities, along with an increased workload at school, can lead to disrupted sleep patterns.

NSF notes that school-age children often “become more interested in TV, computers, the media and Internet as well as caffeine products — all of which can lead to difficulty falling asleep, nightmares and disruptions to their sleep.”

Watching TV close to bedtime has been associated with difficulty falling asleep, anxiety around sleep and sleeping fewer hours. NSF reported that adolescents with four or more items such as TVs and computers in their bedrooms were more likely than their peers to get an insufficient amount of sleep at night. They were also almost twice as likely to fall asleep in school and while doing homework.

If parents have addressed environmental distractions and over scheduling and their child still demonstrates excessive daytime sleepiness and poor sleeping patterns, there is a possibility that the child may be suffering from a sleep disorder. According to NSF, sleep problems and disorders are prevalent at the ages of 5-12.

Insomnia is one common sleep disorder that can affect children. In a survey of children in pediatricians’ waiting rooms, more than 40 percent were reported by their parents to experience some form of insomnia, such as unrefreshing sleep, difficulty falling asleep, trouble staying asleep or early morning awakenings. Changing bedtime behaviors by creating a bedtime routine and setting limits sometimes helps children suffering from insomnia.

Sleep disordered breathing can be a more serious sleep disorder. Snoring is one example of this, and can have several causes such as enlarged tonsils or adenoids. Another more serious cause of snoring can be sleep apnea, in which children snore regularly or loudly, stop breathing, gasp for breath or work particularly hard to breathe while sleeping.

Children with sleep apnea are not able to sleep well through these disruptions, and the lack of quality sleep is thought to increase the risk for daytime learning problems, poor school performance, daytime sleepiness and hyperactivity.

Restless Legs Syndrome (RLS) is another disorder that can impede a child’s sleep. Uncomfortable feelings in the legs can create discomfort and cause the child to move his or her legs, even while trying to fall asleep. According to NSF, children with symptoms of RLS at least a few times a week sleep an hour less each night and are twice as likely to wake up during the night. Parents who suspect that their children may have RLS should discuss the problem with their pediatrician.

Nightmares and sleep terrors are another common problem that can cause children to get poor sleep. Nightmares can be a reaction to change, stress or a scary event. Parents can talk to their child about the dream and any issues the child is experiencing, and make sure he or she is getting sufficient sleep. Sleep terrors usually occur earlier in the night than nightmares and do not fully awaken the child. They can lead to uncontrollable screaming. The child often does not remember these experiences when he or she wakes up in the morning. An irregular sleep schedule, lack of sleep, or stress can cause sleep terrors in some children.

If a child’s sleep disorder does not resolve itself quickly, parents should bring up the subject for discussion with their family doctor or pediatrician.

A study in the Journal of School Health found that some causes of disturbed sleep are reversible, and it is possible for students who suffer from poor sleep to achieve better academic performance after intervention.

Parents can help their children get better sleep in a variety of ways. The National Heart, Lung and Blood Institute offers several suggestions for helping children achieve better sleeping patterns. For example, parents should avoiding overscheduling their child and give priority to adequate sleep.

For younger children, NSF recommends parents implement bedtime routines such as reading together, which can result in better and longer sleep. For older kids, having a set bedtime is associated with an increased likelihood of getting optimal sleep and a decreased likelihood of feeling too tired or sleepy during the day. NSF found that adolescents with set bedtimes before 10 p.m. are much more likely to get an optimal amount of sleep than their peers.

The National Heart, Lung and Blood Institute suggests avoiding heavy exercise and big meals close to bedtime, staying away from caffeine within six hours of bedtime, keeping the room temperature comfortable, darkening the bedroom and keeping the noise level low at night. The institute also recommends that parents educate their children about the importance of sleep. Keeping a sleep diary is one way for children to keep track of their sleeping patterns. And parents can set a good example for their children by getting their own recommended amount of sleep each night.

It is very important for parents to keep track of the difficulties their child may have in sleeping. Parents must be aware that all children, even teenagers, need more sleep than adults. NSF’s 2006 Sleep in America poll showed that while more than half of adolescents reported not getting the sleep they need, 90 percent of parents felt their adolescent was getting enough sleep.

Parents should stay alert for symptoms of sleepiness in their child, and can ask teachers if their child is sleepy or falls asleep during class. Since children tend to get less sleep per day as they move into adolescence, determining early on if a child has sleeping disorders or difficulties can help set the tone for a more positive transition into the teenage years.

The Mayo Clinic pointed out that good-quality sleep can help children learn more easily and reduce many behavioral problems, as well as boost their energy and enthusiasm.

Taras noted, “Overall, we know that children need to be healthy in order to learn at their highest potential. Sometimes children suffer from a chronic disease that cannot be helped, and in those cases parents and teachers and children themselves can only do the best they can, considering the circumstances.

“But in most cases, it is not a chronic health issue, but one that is resolvable, such as getting enough sleep or exercise, eating breakfast or addressing extra pounds. Children can’t tackle these issues alone; they need parental support.”

Those who are interested in learning more about sleep disorders can attend a free lecture presented by Yale-New Haven Hospital (YNHH) Auxiliary on Thursday, October 5 in the hospital’s East Pavilion Cafeteria from 6-8 p.m.

Vahid Mohsenin, M.D., attending pulmonary physician at YNHH and director of the Yale Center for Sleep Disorders, will speak on sleep apnea and treatments and medications for improving the quality of sleep. Refreshments will be provided.

Yale-New Haven Hospital is located at 20 York Street in New Haven. To register for the lecture, call 203-688-2000.

Parents can also learn more about causes and effects of sleep deprivation and ways to help their children sleep better by visiting the National Sleep Foundation’s website, www.sleepfoundation.org.