The timeline on the DVD *confirms* canon;

[Sally]

No: HPFGUIDX 56024

--- In HPforGrownups at yahoogroups.com, "psychic_serpent" 
<psychic_serpent at y...> wrote:
> Given that most Muggle-born families we hear of (Hermione's, 
Lily's, 
> Justin's, Colin's) are rather pleased to have a magical person in 
> the family, if it means that student foregoing a year of Muggle 
> school and starting Hogwarts instead, I hardly think they're going 
> to complain.

There is always the possibility that Hermione skipped a grade or 
started early in Muggle school, which would mean she wouldn't have to 
miss any more than other Muggleborns. Somehow this seems very likely 
to me. ;)

And hey. We're talking about a magic quill here. It probably knows 
when the kids are ready, much the way the sorting hat knows where to 
put them. Hmm... completely unrelated thought... maybe the quill was 
Rowena Ravenclaw's?

~Sally~