Well looking at the photographs from above it hardly looks like a tiny house, especially as it's just the three of them living there. I'm sure it would've been a very comfortable place to live.
At the boarding school I worked at, the head teacher's house on the school grounds wasn't just for him and his family to live, it was also used for school-related and social events, and the downstairs is likely to be spacious to accommodate that. I remember the headmaster and his wife hosting afternoon teas or dinners for groups of students quite often, and I guess it was just one reason why he knew the students well. There were also some events where parents and/or staff were invited too. I'm sure head of these sorts of schools will be hosting all sorts of people throughout the year in their home, so the school of course will want to ensure it is well decorated and furnished.
As a separate point, I did wonder if the next/future heads of EC would want to live in this particular property knowing what has happened in there recently. I did wonder if the school will even end up bulldozing it and building a new property somewhere else on the grounds, given the existing one will always now be associated with such an horrific event.