"Six to eight year olds ate junk food while gaming more than 9 to 12 year olds did." "For 6 to 8 year olds, snacking habits in boys and girls..."

[hardyweineberg]

"Six to eight year olds ate junk food while gaming more than 9 to 12 year olds did."

"For 6 to 8 year olds, snacking habits in boys and girls were exactly the same, whereas 9 to 12 year old boys attending public schools were more likely to indulge in snacks during their gaming sessions than 9 to 12 year old girls going to private schools."

1) Is it grammatical to use "more than" in that way?

2) For the 2nd sentence, it grammatically correct to say "for 6 to 8 year olds"?

3) Is it "attending public school" or "...public schools"?

 

[Tarheel]

1. Yes.
2. The original is fine.
3. Attending public school.