Black Forest Peak has won at the minimum of 42 of its last 44 matches. If one only takes this tournament into account. They won 3 out of 4 matches each in both this years and last year's tournement. Before their loss to Pravda last year they had won at least 39 straight tournament matches. Just getting to the finals in most sports is a sign of a good team.
The other schools might have other specialities than just tanks. I would think the French based school with be a culinary academy. Smaller student population, but large money put into it by the parents and student...and maybe even the industry itself. Plus there could easily be other schools that are not national themed, nor partake in tank tournaments. How many high schools are there in Japan and how large is the combined student body? Is it more than 16 city carrier's worth?
Ooarai doesn't seem to have anything the school is known for, so it would receive less applications over the years. Because it is a girls school, one would guess it isn't a regular public school (do they even have that sort of difference in Japan?) And schools like that generally need something that draws in students to stay open. (Where do the boys go to high school?)
And thus if closed the girls would be transfered to some other school.
There are schools that are around because the get students due to their sports teams. There are others for their acedemics or specialty courses the school is known for. Ooarai seems to not be particularly known for anything save not having a tank course these last two decades (the reason Miho entered the school in the first place). With Hana around you might suspect the school has a vibrant Flower Arrangement program, but there is no evidance such a thing exists as a notable feature of the school.
And Pravda's clear spaces just mimic the actual ship it is based on. The front part is ramped upwards so you couldn't put building on it as easily and maintain "the look" of the carrier
Kiev. Also it is Russian themed. The open spaces might be their "Siberia"
