This scenario represents a violation of Semaj and Kevin’s Fourteenth Amendment rights.
The Fourteenth Amendment includes the clause of equal protection under the law, which can extend to students' rights to express themselves, including their choice of clothing, especially when it pertains to a social or political statement. The teacher's retaliation against Semaj and Kevin for their choice to wear green in support of an environmental cause appears to be a suppression of their rights to free expression.