Simplify the following text for a Grade 8 native English-speaking person.
Original: In reaction to Charles VII Valois 's coronation as French King in Reims cathedral on 17 July 1429 , Henry was soon crowned King of England at Westminster Abbey on 6 November 1429 , followed by his own coronation as King of France at Notre Dame de Paris on 16 December 1431 , although it was n't until a month before his sixteenth birthday on 13 November 1437 that he obtained some measure of independent authority , before he finally assumed full royal powers when he came of age .
Simplified: Henry was eventually made King of England at Westminster Abbey on 6 November 1429 a month before his eighth birthday . He was made King of France at Notre Dame in Paris on 16 December 1431 .