'Catalogue Sites' allow tutors to register and offer their services from one site. This may give the impression that the tutors belong to a single organisation. However, teachers are frequently self-employed individuals and levels of vetting vary widely from site to site.
Examples of Catalogue Sites
First Tutors provides both local (in the UK) and online tuition in a number of subjects. It caters for 'primary, secondary and degree level private tuition or home tutoring'.
Tutor Hunt is a UK based tuition directory service covering all levels and locations. They cover a broad range of subjects.
Tutor Hub facilitates peer-to-peer help through free-to-use forums as well as providing fee-based online tutors in a variety of subjects.