Puberty and secondary sexual characteristics
Biology · Key Stage 3 · The School
What triggers puberty
Puberty begins when the body starts to release more of certain HORMONES. Hormones are chemical messages carried in the blood. Before puberty, these hormones stay at a low level. Once they rise, they trigger a set of body changes. Those changes spread out over several years. Puberty is not one sudden event.
Secondary sexual characteristics
The reproductive organs are present from birth. These are called PRIMARY sexual characteristics. SECONDARY sexual characteristics appear later, at puberty. They differ between males and females. In males they include body and facial hair, a deeper voice, and broader shoulders. In females they include breast development and the start of the menstrual cycle. Both sexes also have a growth spurt. This lesson covers the outline the science curriculum requires. Families and schools differ on how and when the detail is taught, and any question you have belongs with a trusted adult — a parent, a carer, a teacher or a school nurse — not this page.
Why the timing varies between people
Puberty usually starts somewhere between age 8 and age 14. The exact age is different for each person. Genes, health and diet all play a part. Starting earlier or later than a friend, within this wide range, is normal. It is not a sign that anything is wrong.
Suppose a class asks how far from the average a normal start to puberty can be. They use real figures for girls from the National Health Service in Wales. The average age to start is 11. Any start from 8 to 13 is normal. Step 1: the range is 13 minus 8, so it is 5 years wide. Step 2: the early end is 11 minus 8, so 3 years before the average. Step 3: the late end is 13 minus 11, so 2 years after it. For boys the average is 12 and the range is 9 to 14. The same sums give 5, 3 and 2 again. Both ranges together give 8 to 14, the range on the National Health Service website for everyone. That is 6 years wide. So a start 2 or 3 years from the average can still be normal. The health service in Wales says there is not usually any need to worry if puberty does not start around the average age. Any question about your own timing belongs with a trusted adult.