What grade is Donald in?

[unseenclass]

They keep saying he is Virginia's older brother but he seems to be a freshman like her?

[Kurisu No Patto]

He is the brother of William and Virginia, almost a year older than Virginia but in the same grade level at school. His birthday is in October.
Source: Magical Diary Wiki [magicaldiary.wikia.com]

[Hanako]

Right. His birthday is in October, and Virginia was born prematurely (her birthday is in the summer) which results in them being near the same age.