I suppose you could. But the flip side is, you've also got four years of "every grade counts" to endure. That's a lot of pressure to put on a 13/14 year old. If you tank in grade 9, you'll never have another chance to bring that GPA up as high as it could have been. If it'd been me (considering my woeful grades in Grade 9), I'd have just given up and decided I wasn't the "academic type". But, I managed to graduate with the top average in my class, because - fortunately! - they only counted my final year.
Whereas, if you have a family tragedy in Grade 11 here, you can just take a thirteenth year and redo a bunch of your credits and it won't hurt your chances of getting into a good school.