UPDATE 23/11/2020: In May 2020, Oxfordshire County Council withdrew its trans-gender toolkit, pending legal action. In the light of this decision, I recommend that schools speak to their legal provider before making policy decision with regard to supporting students who identify as trans-gender. (For the Oxfordshire case, see here: Oxfordshire council transgender guide scrapped after girl's court case)
Talking to colleagues around the country, many schools are seeing pupils who are describing themselves as transgender. This raises a number of issues when supporting transgender children in schools. This is not a topic within my personal experience, but colleagues who have, recommended these websites and resources to find out more.
Organisations
The Gender Identity Research and Education Society (GIRES)
Directory of local groups
Resource Packs for schools
Trans* Inclusion Schools Toolkit (Brighton and Hove)