Many students between the JSS and SSS levels do not know that mathematics has timing, when it comes to personal study or preparation. There are different times students assimilate mathematics and these times vary from one student to another.
Within the last half a decade, I have seen students who took personal study of mathematics at different times and it increased their performance greatly. Some only take personal study of mathematics in the evenings (after normal school hours), while some had theirs late in the night (when everyone was asleep and the house is quiet). Some prefer to sleep at night and wake up to study at midnight. Some others still prefer to take their own study very early in the morning before getting ready for school. I have seen students who only made use of the break time in school to study mathematics.
The unfortunate situation is that, despite the few examples I've seen and highlighted above, many students still perform badly in their mathematics. In my own personal study and research, I have linked one of the failure factors of students in mathematics to this problem of not "knowing the right time to study mathematics".