A teacher does not forfeit his right to engage in religious activities on his own time, away from the school campus. Teachers may not be prohibited from attending church, even if one or more of their students attend the same church. Away from the school, the teacher may attend religious activities with his students, may lead his students to Christ, or teach them in a Sunday school class, at which time the teacher is free to discuss all religious matters with them, including devotionals and proselytizing. The teacher may also serve as a church youth leader outside of school time, even if his own students are part of the youth group. When a teacher is not actually on contract time for the school, the restrictions of the Establishment Clause do not apply.
While a teacher may not invite students during his contract time to attend church or other religious activities, the teacher may contact the student’s parents on his own time to invite the student or the parent to church. The teacher should make clear that the invitation is being extended on a personal level and not in his capacity as the child’s teacher. The teacher should also make clear that the parent’s or child’s reaction to the invitation (whether positive or negative) will have no bearing in class. Anytime a teacher interacts with his students on a religious level away from school, the teacher should make certain the student understands the teacher is not acting as a representative of the school, but is acting as a private individual.
Teachers need to be very careful, however, even when engaging in such interaction away from school since some courts have said that a school may prohibit such interaction.
—Keeping Christ in America’s Public Schools, Gibbs & Gibbs, 2008