I have 3 years experience as a O level math and science tutor. I have had an O level math student whose grades improved from 10/100 to a pass within 6months despite having failed math since sec 2. I have other O level students whose science improved from Cs to Bs or As. I have also taught JC H2 Math and Chem for the past 4 months and the student's grades improved, especially for Chem (from C to A) for her promos.