I've been a member of the Incorporated Society of Musicians (ISM) since I started teaching. Essentially there's a choice of two 'unions' for musicians, the ISM and the Musicians' Union, both offering support, advice, legal protection, training, online communities and real-life meet-ups. I've benefited from the ISM's resources for teachers - I use a version of their teaching contract - and I couldn't (legally) do my job without their Public Liability Insurance (although I've thankfully never had to claim on it!). They run regular webinars which have given me some interesting food for thought on topics such as 'teaching in the digital age' (how do we keep the attention of children who are used to social media and computer games?), career planning and psychological wellbeing for musicians.
Their blog is a great resource of ideas and opinions from different musicians, too, and I've particularly enjoyed the new Teacher Focus series, where a private teacher writes about their own job, thoughts and experiences. So I was very happy to answer a call for more contributions to this series, and reflect on my background, principles of teaching and hopes for the future - you can read my post at https://www.ism.org/blog/private-teacher-focus-rachel-shirley.
Flute player and teacher blogging about playing, learning, teaching and researching music.
The Reliable Musician - a series of blog posts on the skills that make the sort of musician people want to work with!