Sometimes the key to better grades is simply this: get enough sleep. Sleep deprivation (i.e. not getting enough sleep) causes a whole host of problems, from increased blood pressure to impaired brain function. This has consequences both in the long-term (for your health) and in the short-term (for your studies and career). If you don’t believe me, take a look at this helpful chart.
When I was in JC, I averaged 6 hours of sleep per night, with occasional afternoon naps thrown in. I did decently for my A-levels, but it was in university that the A’s really starting rolling in. The difference? I had learnt, while I was serving in the army, that sleeping well made my brain function on a profoundly higher level.
So if you want those A’s? Get enough sleep.