Based on a popular light novel.
from Baka-Updates Manga:
The protagonist is a guy who is among the stupidest of the stupidest in the school. In this school, your grades can, under the supervision of teachers, take a virtual form to do combat! However, if you leave an examination half way, you get zero marks. A bright and cute girl, Mizuki Himeji, was having a high fever during the examination. Despite her potential to be the second highest scorer in the level, she obtained zero marks for having left due to her illness and is thus allocated to the worst class, class F.

Grades mean almost 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-cons, refrigerators, adjustable seats and all kinds of different appliances. Within the refrigerator, there are all kinds of drinks and snacks. Their ceiling is made of glass, the wall lets them put up high-class drawings and plants.

As for Class F, the worst class... They have Japanese desks and seat paddings. Their blackboard is dirty and there is no chalk even! Someone complains that the legs of his desk are broken, so the teacher asks, "Didn't we distribute some glue to stick wood together? Glue it back yourself later." Another one complains that wind is blowing in from the broken window. The teacher says, "I got it. I will apply for plastic bags and invisible glue to fix it later." There are spider webs everywhere, not a patch of the wall is clean. A unique moldy smell spreads across the entire room; it must be from the old tatamis used to tile the floor. This is the status of class F.

The protagonist feels displeased at such an arrangement, and seeks help from his friends to try to make a change through summoning war!! And they devise all kinds of plans to try to beat the famous class A, intending to get class A's classroom and equipment if they win!!