Simplify the following text for a Grade 7 native English-speaking person.
Original: On 21 October 1966 , it became known for the Aberfan disaster , when a colliery spoil heap collapsed into homes and a school , killing 116 children and 28 adults .
Simplified: Aberfan is a village in South Wales where , in 1966 , a slag-heap fell down , killing 28 adults and 116 children .