The number (and rate) of qualified teachers that enter and leave service (from state funded schools in England) in each year are publicly available.
The latest statistics, for 2011 to 2015, are in Table 7b in the statistical first release ‘School Workforce in England, November 2015’, which was published in June 2016:
In 2015, 43,070 full-time equivalent (FTE) teachers left, but they were replaced by 45,810 new entrants. Of those who left 34,250 FTE teachers were ‘out of service’ (meaning they are not currently teaching in state funded schools) and 8,820 FTE teachers had retired.
We are actively addressing the key issues that evidence suggests cause teachers to consider leaving the profession – for example by supporting schools to reduce unnecessary workload and improving behaviour management training for new teachers.