Around chapter 100 to 130 of the manga,
Yoshinaga Hiroko and Urakawa Minori went to Nagoya to attend SKE48 as a part of their role as the international member.
While the school knows that Yoshinaga is a member of AKB48 and thus there would be no problem with her skipping class for days, they didn't know that Urakawa Minoru is also a member.
Since going back and forth from Nagoya to Tokyo everyday is certainly not possible, considering that
Minoru was performing 3 times a day in the park.
How did Minoru was able to skip class for a whole month without causing the school to contact his parents?