I'm very sorry for your case Aldo. The only way that makes the embassy right is if your father finished the school without a break from work (written on the diploma) because that is explicitly stated in the rules, otherwise I don't see any problem with the diploma. During the communist era people's education was chosen by the government and not at their will, and I think the embassy needs to understand that.
No my father didn't work during his high school years.
@SusieQQQ , What rules? I've written in my first post that I know people who have finished only High School and they did not work in their entire life. Why people who have finished High School and have no work experience are prior to people who have finished equivalent to High School and have more than 25 years of work experience for US government people??? Logically this is the truth because this year I know people who got visa. Main applicant finished high school and haven't worked in his life.
From one point I think that they refused the visa for another reason and they just doesn't tell me.
Days before the interview I got a very strong bad feeling about interview, and it turned out that that bad feeling was true. I'm having the same feeling about the reason why they refused my family's visa. I'm very skeptic about these thing but I do not know why I have this bad feeling.