Child domestic workers are particularly vulnerable to trafficking, forced labour, sexual violence and many health issues.
There are more than 168 million child labourers - 11% of all children in the world - who are working instead of learning.
An estimated 246 million girls and boys are harassed and abused on their way to and at school every year - with girls particularly vulnerable.
In Africa, half of all children said they had been bullied at school.
About 16 million girls aged 15 to 19 and some one million girls under 15 give birth every year—most in low- and middle-income countries, according to the World Health Organization.
Not only is this a violation of their human rights, it is also one of the most common causes for girls to drop out of school.
There are child marriages in every part of the world, including Europe and north America.
But the highest rates of girls under 18 getting married are in Niger (76%), Central African Republic and Chad (both 68%).
On International Day of the Girl Child, here are 13 reasons why girls continue to be denied an education.
Too often marriage is seen as a higher priority than education.