How can sociology be useful within this topic? "Why people cheat".
Yet another way to look at this issue from a sociological perspective is to frame it in terms of individual motivations and deterrents, and how they affect a person's actions in society.
For example, a person who is motivated by socialization that teaches us good grades are important may be motivated to cheat on an exam because society will reward him/her for it as long as they are not caught. The motivation to cheat increases if the chance of being caught decreases, and vice versa. A person may not think twice about cheating on a worksheet, but wouldn't dare cheat on a bar exam, thus the deterrents set in place by society work directly against the motivations we may have to cheat, especially the more serious the penalty gets.
This is simply evidence that many in society are more afraid of performing poorly than they are of being caught cheating, and that the deterrent level has to be set quite high in order to overcome that fear of poor performance.
A sociologist might also do a study on the limitations conscience places on our actions in situations where being caught cheating is unlikely.
One major aspect of sociology is its attempt to determine how society, rather than individual psychology, affects the ways in which people behave. It is this aspect of sociology that would be helpful in answering the question you pose.
A sociologist would try to determine what kinds of people cheat and would then look at whether those kinds of people are in some way influenced by society to be more prone to cheating. (Or they could go the other way and ask why other kinds of people don't cheat.)
A possible example would be that a sociologist would find that men cheat more than women. The sociologist would then ask what there is about our society that influences men to cheat and/or women not to cheat. This would be sociological because it would look at the impacts of society on the ways individuals behave rather than looking at personal psychology or biology or other such factors.