I have been a tutor since 2004, taking mostly secondary English and Biology/Science assignments or primary English, Science and Tamil.
I believe in teaching students not just content, but how they can process the content and be able to study independently. I teach them studying techniques, and for English, how to write and read better, instead of merely drilling on test papers.
Most of my past students, whom I tutored in science, have left being able to develop understanding of difficult concepts on their own. And all of them have improved at least two grades, with some getting As and Bs where they failed or got Cs before.
And my English students, even in my group tuition, have pulled up their grades significantly through better essay writing and better inference skills.