Concentration is when you are conscious about what you are reading or listening which mean you understand what you are learning when you learn it, the question is, how to increase the time you understand what you are learning?
The worst lack of concentration is when you decide to leave studying and postpone it to some other time, this is when you should learn how to concentrate in studies for long hours
The most important fact about concentration is to keep sitting for long hours, and to do so you should:-
If the environment you are living in suffer form sound pollution:-
Which make you unfocused on what you are studying, you should get used to these sounds and filter it with your mind by not focusing on it and being bothered from it, this only come when you believe and admit that you are deficit to change the environment around you but you can change yourself to cope with environment.
Knowing that you are deficit to change people, things or places to an extent, is so essential to get higher marks than your friends, the one and only thing you are not deficit to change is yourself, that's why you should keep changing yourself so that you can concentrate on what you are studying the best as you can.
This is when your dream is the most precious thing you have, so that you have to protect it the best way you can.