***** NOT A TEACHER *****
Hello. Gorkem Atay:
As I understand it, there are three acceptable ways to say that:
1. It is important that everybody be told the truth.
2. It is important that everybody should be told the truth.
3. It is important that everybody is told the truth.
Here in the United States, #1 is still the preferred way.
"Be" is called the subjunctive.
One uses the subjunctive when referring to something that is not a reality.
Maybe these examples would be easier to understand:
4. I demand that you be / should be/ are at the office by 8 a.m. tomorrow.
a. I am talking about tomorrow.
b. I am talking about something that I demand.
c. Maybe you will not obey my demand.
d. There is no reality to that sentence. So that is why Americans usually would not use "are." "Are" refers to reality: "They are at the office now."
Student or Learner