SOUTHLAKE, Texas — Officials at a North Texas school say an Election Day civics lesson for some third-graders inadvertently included a sexually explicit videotape.

Some students at Johnson Elementary School in Southlake saw the video as they were leaving an auditorium Tuesday. School district officials said teachers had removed an unmarked tape from a video player and played a lesson on the three branches of government.

Afterward, a teacher returned the original video to the VCR. That adult video — which included pornographic images — began playing as teachers led students out of the auditorium.

Officials said the video was quickly stopped and that most students didn’t see it. The video player hadn’t been used since last month, when vandals broke into the school.