The same idea can sound casual or formal depending on word choice. In a job interview, which is the most formal way to refer to young people?

"Children" is the neutral, formal term for young people, appropriate in professional or written contexts like a job interview where precise, respectful language matters. It avoids the casual tone that could seem out of place when trying to present yourself professionally.

"Kids" is a common, casual synonym perfectly fine in everyday conversation but slightly too relaxed for formal settings, and "guys" is very informal slang, typically used for addressing peers directly rather than referring formally to young people in general.

This kind of register-matching — choosing the more formal synonym for formal settings — applies across huge swaths of English vocabulary, which is why interview coaching often focuses heavily on word choice, not just content.