Of course you only had a thousand students through all those six grades.
( ( Of course ) ( you ( only ( ( had ( ( a ( thousand students ) ) ( through ( all ( those ( six grades ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN Of) (NP (NN course))) (NP (PRP you)) (ADVP (RB only)) (VP (VBD had) (NP (NP (DT a) (CD thousand) (NNS students)) (PP (IN through) (NP (PDT all) (DT those) (CD six) (NNS grades))))) (. .)))
For all the six grade there was a thousand students.
( ( For ( all ( the ( six grade ) ) ) ) ( there ( ( was ( a ( thousand students ) ) ) . ) ) )
(ROOT (S (PP (IN For) (NP (PDT all) (DT the) (CD six) (NNS grade))) (NP (EX there)) (VP (VBD was) (NP (DT a) (CD thousand) (NNS students))) (. .)))