"Sophomoritis" is the term educators apply to people who are immature and over-confident.

Sophomoritis

A colloquial term referring to an attitude of overconfidence displayed by some second-year students (sophomores), often characterized by a lack of respect for others' opinions or a dismissal of established facts.

Immature

Lacking in development, either physically, emotionally, or intellectually; not fully grown or developed.

Over-Confident

Describes a state of being excessively confident without sufficient reason or evidence, often leading to miscalculations or errors in judgment.