Teacher-Librarians in Canada come to that role in a variety of ways. All are teachers first and then add additional qualifications. In Ontario, teachers can take three courses to get a School Library Specialist certification. In BC, many teachers take a diploma (8 senior undergraduate level courses in teacher-librarianship). At my own university, the University of Alberta, students can either take an MLIS degree which prepares them to work in all types of libraries (but primarily academic and public libraries) or our Master of Education degree with a focus on teacher-librarianship.
There are others that work in libraries, of course, library technicians (those with a two year diploma from a college program) are much more common that qualified teacher-librarians in Alberta. There are also professional librarians (those with an MLIS degree) but without a teaching qualification who also work in school libraries.