Dr. Randolph Nuñez, pediatrician at Lincoln Hospital.

As students from pre-K to college head back to classes, Dr. Randolph Nuñez, a pediatrician at Lincoln Hospital, shares some tips to help young people have a healthy and successful school year.

Q. Schools require that a student's immunizations be up to date. What immunizations does a child need, and when?

A. Children need immunizations according to three major age groups: birth to 15 months, 4 to 6 years old, and 11 years old. From birth to 15 months, children receive multiple vaccines to protect them from pneumonia, diarrhea, polio, tetanus, Hepatitis B, measles, mumps, rubella and chicken pox. We're lucky to have combination vaccines now so children don't have to receive large numbers of injections.

At 4 to 6 years old and again at 11, children need booster vaccines against these same diseases. At age 11, we also recommend that children receive the meningitis vaccine and the HPV vaccine, which in females prevents cervical cancer and in males prevents genital warts. We also recommend the annual flu vaccine for everyone starting with babies at 6 months old.

Q. Where can children get these immunizations and how much do they cost?

A. Families can visit their primary care physicians or get basic child and teen health services from an experienced physician, including immunizations, at HHC Child Health Clinics in all five boroughs of the city. HHC makes sure that New Yorkers have the opportunity to be immunized against disease regardless of ability to pay or immigration status. All immunization services are available at little or no out-of-pocket cost. For a list of HHC Child Health Clinics go to our website at www.nyc.gov/hhc

Q. You have an easy way for children and parents to remember some good health guidelines. What is it?

A. It's the 5-2-1-0 rule:

• Five servings of fruits and vegetables a day.
• Two hours of screen time. That's all screens: television, video games, cell phones and computers - unless you're doing homework. Studies show that kids who are exposed to many hours of screen time have decreased school performance.
• One hour of exercise.
• Zero candy, juice or soda. They are loaded with sugar.

Q. What can busy parents do to make sure their children are eating healthy foods?

A. We do understand the time constraints. But everybody has to eat, and it's important to make good choices. Parents need to set the example, because kids notice these things. At every meal you want to have healthy choices: for example, chicken, vegetables and an apple for dessert. Involve children in the process of making food. And introduce one new food per month. With smaller kids you have to be persistent. Sometimes it takes a few tries for them to get used to the texture and taste.

Q. What if a child isn't particularly athletic? How do you get them to exercise?

A. Participating in school sports is the easiest way to get a youngster involved physically. But there are other ways. Go power-walking or jog or do other exercise on your own or with a group of friends. Take advantage of free programs offered by the New York City Parks Department and low-cost programs offered in your community. And work exercise into your daily activities: walk your pet; walk to school; and use the stairs instead of elevator. Exercise is an excellent way to ward off obesity, and we know that if we address this issue when a person is young, they are less likely to be obese as an adult.

Q. How much sleep do children and teenagers need?

A. Sleep is a basic need. Sleep deprivation leaves children tired, easily distracted and moody. Children in elementary and middle school need about 10 hours a day. And teenagers need nine hours a day. This can be difficult with the increasing demands of school, work and a social life. Still, it's important to let our bodies and minds rest for the appropriate amount of time so we can function well the next day.

There's no question that healthy eating habits, exercise and sleep have a positive impact on school performance and help you feel better about yourself. These are the things that will give you an easier road to a successful life.