Which action is likely a Level 'D' violation?

A Level 'D' violation is typically the most serious category of violations involving actions that pose a significant risk to the safety and well-being of others. Assault on another student falls directly into this category because it involves physical harm or the intent to cause harm, which undermines the safety and security of the environment for all students. Such behavior is unacceptable and warrants the most severe disciplinary consequences.

The other options, while they may also represent violations, do not reach the severity of physical assault. Wearing an incorrect uniform might be a violation of dress code but does not threaten anyone's safety. Using disrespectful language, although harmful to the interpersonal dynamic, lacks the physical danger associated with assault. Excessive tardiness reflects issues of responsibility and time management but poses no immediate threat to others' safety. Therefore, assault, with its potential for severe harm, is rightly classified as a Level 'D' violation.