The latest annual Good Childhood report from the Children’s Society measures children’s subject well-being and happiness. It has their opinions on social media, friends, family, education and health. It is possible to get breakdowns by gender. Details of the methodology used is provided on the website. Trends in time from the first index in 2005 are also mapped.
For a broader insight into the material conditions of children in other nations see the global UNICEF annual State of the World’s Children report.
And the 2017 End of Childhood report from Save the Children which documented how many children miss out on childhood due to war, forced marriage and poverty.