See, i can understand that 11th class is difficult at times and even by studying harder and harder and practicing for the same thing many times, may be your scores are same for a while, but i assure ypu if you keep up your practice it will bore you good fruit.

Think it like in this way ( i used to think this way when i was in 11th), your marks are not increasing it means that there's some fault and if there's some fault or lack of practice you should find that spot by analysing your test scores and the answers you have given to them and then after that clear your concept on that topic, solve as many problems as you can and then again give test...i issure you will score good next time.

See 11th is interesting ( as i think so) it's just you have to clear your concepts, itsi all about concepts and not about cramming.