文部科学省は、病気などの理由以外で、１年に３０日以上学校を休んだ子どもが、２０１６年度に１３万４３９８人いたと発表しました。
The Ministry of Education announced that there were 134398 children in the 2016 school year who had more than 30 days of absence for reasons other than illness.
The meaning is clear (I think) but the で after 以外 is confusing me. I'm familiar with two uses of 以外:
What is the function of で in this sentence? How would the meaning change if I replaced で with に?
「文部科学省{もんぶかがくしょう}は、病気{びょうき}などの理由以外{りゆういがい}で、１年{ねん}に３０日以上学校{にちいじょう}を休{やす}んだ子{こ}どもが、２０１６年度{ねんど}に１３万{まん}４３９８人{にん}いたと発表{はっぴょう}しました。」
In this particular context, only 「理由以外で」 would be correct and natural-sounding.
The sentence states what happened for the reasons other than illness. In other words, 「病気などの理由以外で」 modifies 「学校を休んだ」. It is of a reason-and-result type of structure.
If it said 「理由以外に」 instead, the readers would expect that the enumeration and/or explanation of the other reasons would follow, which obviously is not the case here. Interestingly enough, though, you yourself stated:
- A以外に... = Besides A ...
which is correct. One would expect an enumeration to follow that.
で is used simply because で is the normal particle you should use after 理由 when you want to adverbially say "for ～'s reason". 理由に is acceptable only when used in the ～を～に pattern. Here 以外 does nothing about the particle choice; it can reverse the meaning without changing the particle choice.
Other examples of using 以外 with arbitrary particles:
These sentence are still grammatical if you removed 以外 (of course the meaning will be reversed).
