I have taught 3 students in Secondary School Additional Mathematics and Economics, Junior College H2 Economics.
The JC student was retaking his 'A' Levels for H2 Economics. He got a decent grade of B for the subject, which was a great improvement from his previous exam.
As a student who just left JC a few years ago, I am still in touch with the syllabus. Besides, I am studying double degree of Engineering and Economics in NUS. This means that I am still doing high level mathematics and economics, putting me in an even better position to teach.
Also, I often have no qualms about staying back longer and even answering questions through email or phone. I am patient and firm with my students, and I always prepare additional assignments for them to assist in their understanding.