Hello. Just to clarify, as it looks that English isn't your first language, but "minoring", do you mean "downplaying" or "minimizing"?

If you're talking a non-university school, a grade school or primary school, it's because there's so much to talk about. Elementary schools are designed to provide a baseline education, which means they should deal in trends and themes, not specifics.

In addition, because curriculum tends to be larger than the time allotted to teach it, I've seen "world history" classes that failed to get beyond the 19th century because the semester ran out. Even in classes that teach to the present day, there will be a tendency to accelerate the pace toward the end in order to reach completion. That means all but the largest events get pushed to the wayside.

In specialized classes, secondary school or post-secondary education, there is specialization -- specific classes focusing on specific topics. If you selected a class whose focus includes the history of Israel or the history of the Middle East, you should touch on the Balfour Declaration.

And as a final note, teaching is always dependent upon the teacher. All teachers are human, and they all make mistakes, have gaps in their knowledge, or prefer to teach specific things. If you feel you didn't learn about a subject in school, it may rest with the teacher, rather than the curriculum.