Growth and development - primary school children

The easiest way to measure a primary school child’s growth is to plot their weight and height over time on growth reference charts. Healthy children generally have healthy growth and development patterns. Many things influence growth, including genes, nutrition, general health and periods of illness.

Children do not usually grow at a constant rate. They tend to grow in “bursts”, so a change in height and weight can happen in a short space of time. Overall, growth during the primary school years is slow and steady.

How children’s growth is measured#

Doctors, nurses and other health professionals use several ways to assess growth in primary school children. The most common include:

• standard growth references, or growth charts, which help interpret a child’s height and weight measurements
• body mass index (BMI), a calculation that, used with age-specific BMI charts, gives an indication of the weight-for-height ratio

Growth charts#

Growth charts are used to measure children’s growth. The measurements come from studies of the population as a whole and reflect the normal range of height and weight for children within a particular group (for example, all children born in a particular year). The charts are divided into sections called “centiles”, which show the proportion of the group above or below a particular measurement.

For example, a child on the 85th centile for height is taller than 85 per cent of other children of the same age and gender, but shorter than 15 per cent of them. Different growth charts are used in different settings, and internationally recognized charts, such as those published by the World Health Organization, may be used to assess and monitor children’s growth.

Body mass index (BMI)#

BMI is the most common way to assess whether a person is underweight, a healthy weight or overweight. It interprets a person’s weight in relation to their height and is calculated by dividing weight in kilograms by height in metres squared:

BMI = weight (kg) / height (m)²

As children grow, their amount of body fat changes, and so does their BMI. For example, BMI usually drops during the preschool years and then rises through the school years into adulthood. For this reason, a child’s or adolescent’s BMI must be interpreted together with age and gender centile charts.

BMI centile charts are used for children over the age of two, with the centile cut-offs used as a guide only. A BMI above the 85th centile indicates that a child is overweight, and a BMI on or above the 95th centile indicates obesity.

Why a healthy weight matters#

Being underweight or overweight can cause problems both now and later in life. For example:

• Severely restricting food or dieting before puberty can stunt a child’s growth.
• Overweight children may be teased, which can make them self-conscious and affect their attitude to school.
• Overweight children are less likely to take part in physical activity, which can make it even harder to manage their weight.
• Childhood obesity can increase the risk of developing illnesses such as diabetes and heart disease in later life.

Body image and the role of parents#

Some primary school children believe they are too fat or too thin, even when they are within the healthy weight range for their height and age. At this stage, children become aware of how they look compared with others and start to notice media messages about body image. How parents respond to these concerns is very important.

Parents and carers are the main role models for children of all ages, despite the powerful influence of peers and the media. Some practical steps include:

• Be a good role model and establish healthy eating habits for yourself and the whole family.
• Avoid “crash diets” or skipping meals yourself, and talk with your children about why healthy eating matters for everyone.
• Involve your children in physical activities they enjoy, perhaps doing things together as a family, such as walking or bike riding.

This is an ideal time for your child to learn about the importance of healthy food and activity.

When to see your doctor#

Always see your doctor if you are concerned about your child’s growth. Your doctor can use a range of charts to help assess whether your child’s growth is a cause for concern.

Key points#

• Children’s growth during the primary years is slow and steady.
• Doctors, nurses and other health professionals use a variety of ways to assess growth in primary school children.
• BMI is the most common way to assess whether a person is underweight, a healthy weight or overweight.
• Being underweight or overweight can cause problems both now and when your child is an adult.
• How parents react to their child’s body image concerns is very important.

Where to get help#