What do flashing amber lights under a school warning sign indicate?

Answer: B — They warn you to slow down until clear of the area

Flashing amber lights under a school warning sign indicate that drivers should slow down and use caution until they have completely passed the area. This is especially important near schools as there may be a high volume of pedestrian traffic, such as students and parents dropping off or picking up children. Option A is incorrect because flashing amber lights do not necessarily mean that school is in session, as the lights may be activated at any time for the safety of pedestrians. Option C is incorrect because while there may be a pedestrian crossing nearby, the flashing amber lights specifically indicate a warning for the area ahead. Option D is incorrect because the lights do not necessarily indicate a school event, but rather that drivers should be cautious due to the potential for high pedestrian activity. Therefore, option B is the most accurate and appropriate choice.