those little kids don't understand it
( ( those ( little kids ) ) ( ( do n't ) ( understand it ) ) )
(ROOT (S (NP (DT those) (JJ little) (NNS kids)) (VP (VBP do) (RB n't) (VP (VB understand) (NP (PRP it))))))
The younger kids don't understand the more complex assignments they're given. 
( ( The ( younger kids ) ) ( ( ( do n't ) ( understand ( ( the ( ( more complex ) assignments ) ) ( they ( 're given ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJR younger) (NNS kids)) (VP (VBP do) (RB n't) (VP (VB understand) (NP (NP (DT the) (ADJP (RBR more) (JJ complex)) (NNS assignments)) (SBAR (S (NP (PRP they)) (VP (VBP 're) (VP (VBN given)))))))) (. .)))