How to resign
The procedure for resigning depends on the type of school you serve and your role on the board.
I'm a governor at a maintained school
You can resign at any time by giving written notice to the board's clerk (sometimes called a 'governance professional').
This is under regulation 19 of the governance regulations 2012 and regulation 7 of the governance regulations 2013.
I'm a trustee of an academy or multi-academy trust
You can resign by letting the academy trust know and then giving your official written notice of resignation to the clerk/governance professional. However, there must be at least 3 trustees still in office at the time your resignation takes effect.
This is set out in articles 65 and 67 of the model articles of association for academy trusts from the Department for Education (DfE), but check your own articles as they may differ.