Original: The Itza Maya, Ko 'woj, and Yalain groups of Central Peten survived the "Classic Period Collapse" in small numbers and by 1250 reconstituted themselves to form competing city-states.
Simplified: The maya Itza, Ko 'woj, and Yalain groups of Central Peten survived the "Classic Period Collapse" in small numbers. By 1250, they started to form competing city-states.