Today's New York Times has an article ("Is Junie B. Jones Talking Trash?") about the Junie B. Jones chapter books by Barbara Park. I have only a passing familiarity with the series and had no idea that they were so controversial. Interestingly, at issue is Junie's grammar. The NYT sums up some of the problems: "Her adverbs lack the suffix 'ly'; subject and object pronouns give her problems, as do possessives; she usually isn’t able to conjugate irregular past tense verbs; and words like funnest and beautifuller are the mainstays of her vocabulary."
On one side of this debate is those who find the books to be funny and entertaining. These parents don't see any harm in their children reading the books and are happy their children are reading at all. Some even view Junie's grammar as an opportunity to discuss proper grammar. On the other side of the debate are parents who are outraged about the language in the books because it lays a foundation of improper grammar for children who are still learning the English language.
While I wouldn't support banning these books entirely (Park was on the ALA's 2004 list of Most Frequently Challenged Authors!), I probably wouldn't recommend these books or encourage children to read them. I have to agree with the parent in the article who is quoted as saying “No wonder we have declining literacy and writing proficiency rates in this country!” I work at a university and frequently interact with undergraduates who don't have a grasp of basic grammar or even spelling. Friends who teach courses at various universities confirm that this is increasingly widespread. It seems clear to me that many children become adults who have never learned proper grammar. Junie B. Jones is isn't to blame for this, but she does seem to be part of a larger trend of simplifying language and placing no value on correct grammar. I don't see why we would want to encourage this trend by promoting these books. Grammar, spelling and vocabulary ARE important, because they allow people to express themselves clearly. Additionally, it could be that much harder for those who don't value these things when they are interacting with those who do (such as in searching for a job).
It might seem silly to some to make such a fuss about language in a children's book, but I think this is an important issue to at least consider when deciding what books to recommend or put in front of your own child.