My first couple years here I taught at a high school, so I can give you a few details about the schools from around where I was. The buildings themselves, if they are older (probably more than 20 years) are all painted the same off-white color and tend too look kind of run down compared to a lot of American schools maybe..?. Heating and cooling systems tend to only be found in places like the health room and the teachers room and administration offices. At my school there was no cafeteria, all the teachers ate at their desks in the teachers office, and the students brought bentos (japanese sack lunches) that their moms most certainly made for them and ate at their desks in the classroom.
School rooms had sliding doors to access them, the floors were a wooden tile type, each about 1 square foot, maybe less. the hallways were very wide open meaning they almost always were connected to the outer part of the school, meaning they had big sliding windows that people would leave wide open for some reason even though it would get freezing cold in the winter and there was no heat in classrooms. Students would come in from a huge entry way where they had shoe boxes where they could change their shoes before entering the school. This of course too was always left wide open so freezing gusts of wind could be flowing through the school.
Students would usually stay at school until 7 or so at night depending on their club activities, and the vast majority of them were in club activities. At some schools I hear it is mandatory for students to be in a club activity. Teachers would leave as early as 5:00 or stay as late as 9:00 just depending on a lot of different reasons.
Students were divided into sections and they tend to stay in the same classroom all day and the teachers would move around and come to them. Homeroom would be from I think 8:35 to 8:50 and first period would start at 8:55. (students had to be at school like by 8:30 or something). Classes were 50 minutes long with 10 minute passing periods. Lunch was 45 minutes, and cleaning time was I think a half hour at the end of the day. The students would do the cleaning of the school, there was basically no maintenance staff.
Sorry it is hard to remember every detail since this was quite a while ago. It also might help if you ask more specific questions as you need them, or maybe you should just try and check the accuracy of what you write with somebody. Perhaps you could find yourself a Japanese penpal?