Top left verical line, 第三十三回 :
"33rd time". 第 is the "rd" (or "th" or "nd") suffixes to numbers, called ordinals. 回 refers to repetitions of an event.
Top left big characters 鈴懸祭:
The name of a cultural festival held by the school. I don't know how it's pronounced, but I'm guessing suzuka-sai, from 鈴懸の木 (Plane Tree or Tree of Hippocrates, which interestingly enough has festival associated with it in Greece), one of which stands in the courtyard of the school.
The flag, 熊谷女子高校:
"Kumagaya [my town] girls high school", called 熊女 (bear girl) for short. Hey, now the character rampaging about and holding the flag makes sense!
The right vertical text埼玉県立+aforementioned 熊谷女子高校:
the second part you can see translated above, but the first part means "Saitama prefectural" (立 is the postfix that adds "al" (established by) to words like 市立 (municipal) and 町立 (townal, only that ain't a word in English so we say "established by the town").
Area below the bear with an umbrella, 熊姫:
"Bear-princess". A play on the school's nickname.
Area right below that, 乙女の道は一本道:
"The path of the maiden doth not deviate". I took some liberty with 一本道 (straight path). It seems like this is a famous saying (or a variation of one, that one being 女の道は一本道), so I poetrified it. I won't even get into the implications of how 女の道 can mean red-light district too, because our bear princesses are pure! If you don't believe it, they'll claw your eyes out.
The leftovers are just dates, so no need to go into them. All kinds of interesting things in this poster eh? Not to mention the art. I hope you enjoy this series, because I must admit I'm happy with all I learned this time around.