Hi Danielle,
Is it fiction or nonfiction? For NF, the word count is a little more generous, though most agents and editors prefer to see less than 1000. And most say under 500 or a fiction PB. But the advice I like is to use the word count you need to tell the story, but ensure that every word is actually needed.
Have you had it gone through a critique group? Or posted it on for a critique in our critique section? Usually an outside reader can help you find ways to cut the word count.
Remember, in PBs, every word needs to justify its existence. Most of the times, adverbs and adjectives aren't needed. "Ran quickly" can be "sprinted." A red truck is just a truck, as the illustration will show the color. My big overused words are "just" and "very". Most of the time I don't need them.
So yes, I do think there is leeway, especially if the PB is geared toward the older age range, but make sure you are certain you want a PB and that every word really needs to be there. Most editors and agents say the PB market is for 4 - 8 y/o, but there are definitely exceptions to the rule.