When it has been commissioned by local authorities? It does not supplant the STPCD, since the STPCD does not write, provide or promote job descriptions. Neither do the TDA in their Professional Standards for Post-Threshold Teachers http://www.tda.gov.uk/upload/resources/pdf/s/standards_postthreshold.pdf And the school which writes or adopts it. It depends on how the HT and governors interpret the STPCD and the Standards, for example: Contribute significantly, where appropriate, to implementing workplace policies and practice and to promoting collective responsibility for their implementation. That paragraph in itself could be interpreted as leadership of a subject or aspect.