Only & only by hard work
There is no short cut to success.
Make a time table to study at home and give at least 4 to 6 hours in the beginning to study.
The lesson you read in the school it is must to read at home.
& lesson you are going to read next day,
You must read it at home before you read in the class. It will give better understanding.
Inshallah if you act upon it you will always get A in all subjects.