I'm a qualified teacher, professional tutor, and former strategy consultant. My gap year was quite some time ago: MSc (Econ) London; BSc (Maths & Stats) St Andrews.
Each pupil is different. Some are focused on exams or selective-school admission. Others I have supported from eight to eighteen. Some lack confidence and appreciate the lack of peer pressure. Others are extremely confident and wish to be stretched further.
Most opt for online tutorials - preferring the scheduling flexibility and reduced disturbance - supplemented, if possible and appeciated, with home visits and face-to-face tutorials.
Almost all my work comes from word-of-mouth recommendation. Moreover, the success of all my tutees is entirely due to their effort. I only guide and encourage.
Students preparing for exams benefit from support over at least six months. The first several months building and applying understanding; the final few working on exam technique.
Tutorials last 60 minutes (45 minutes for the youngest and least confident), rising to 90 minutes for those most confident. All A-level students have 90-minute tutorials. Without a looming assessment, tutorials tend to be weekly.
Success, no greater gift.