It was a sentence from a light novel ようこそ実力至上主義の教室へ that I'm reading at this moment. The school is going to hold a special exam where the second grade students have to pair-up with the first grade students to face a written tests, and it was a new kind of exam where the students from a different academic year were involved as a team. The above-mentioned sentence was spoken by the homeroom teacher towards the students.
If I translated the sentence in english, it will be like: "I don’t need to explain the importance of the written test to you once again, but the school (行ってこなかった) friendly interaction with the other academic years, only during the Sports Festival and the Training Camp so far."
I read from here that くらいのものだ means 'only', and のもの can also be interchanged with なもの. That's why I would translate くらいなもので as 'only during'. (it fits with the situation in the story, but I wondered if I have interpreted it properly)
I'm confused with the meaning of 行ってこなかった in that sentence, is it came from 行く or 行う? And it was the students who didn't have much friendly interaction with the students from the other academic years, not the school itself. But that sentence mentioned the school instead of the students, it makes me doubt whether I have made a wrong interpretation of that sentence.
Please kindly give me your guidance. Thank you.