This manga was added as an add-in to Shounan Jun'ai Gumi and later rereleased separately. Some time later GTO came out and the two prequels became more famous.
Grades mean nearly everything. For Class A: They have a smart-looking teacher, a plasma TV as big as the entire wall as their blackboard, personal laptops, personal air-conditioners, refrigerators, adjustable seats and all kinds of different appliances.
As for Class F (the worst class): They have Japanese desks and seat paddings. Their blackboard is dirty and there's even no chalk!
The protagonist feels displeased at such an arrangement; he seeks help from his friends to try to make a change through invoking war! And they devise all kinds of plans to try to beat the famous Class A, scheming to get Class A's classroom and equipment if they win!!