Is it permissible to supplicate for success in exams despite poor performance?

Supplication (Du'a) is a lawful means to achieve what is desired, and it is permissible in all circumstances. A Muslim must employ the means that lead to their objective, along with supplicating and imploring God. Supplication is one of the most potent means, and it is incorrect to say that it is useless. Rather, it is like eating and drinking in achieving what is desired, as the Messenger of Allah (peace and blessings be upon him) said: "There is no Muslim who supplicates with a supplication in which there is no sin or cutting off of kinship, but Allah will give him one of three things: either He will hasten his supplication for him, or He will store it up for him in the Hereafter, or He will avert from him an evil equivalent to it."