This may have been a typically lame Kerry attempt at humor. It is possible that he was poking fun at the President's poor grades at Yale (which in fact were higher than Kerry's own Yale grades according to the Globe). The source of the video is this California TV news clip. The clip does not provide context.
Hat tip: BOTW Today
UPDATE: MSNBC news has this story:
A source close to Kerry tells NBC News that he was trying to make a "tough and honest joke" about Bush and that in the process he omitted two words which changed the intended meaning. Per the source, Kerry meant to say that he can't "overstress the importance of a great education" and that "if you don't study, if you aren't smart, if you're intellectually lazy... You end up getting us stuck in a war in Iraq." Kerry mistakenly dropped the "getting us" from his initial remarks.Would that our junior Senator posessed enough grace, integrity, and courage to simply say this himself in public. But such expectations are too high for Kerry. Instead he maintains a facade of infallibility (much like W's behavior, isn't it?) and just leaks his excuse to a friendly media source through an aide.