You can generally use both of them,as they are both grammatically correct,but,in short," has changed" is a way of stating that a change has occured,while " has been changed" implies that someone or something has made that change.

Has been changed or is changed?

When you're talking about the act of changing, you have to say "It has changed" (and you're talking about the time that it changed). But if you say "It is changed", you are talking about the state after the act of changing. For example: The policy has changed (referring to the time that it changed).

Has been changed which tense?

Has been changed It gives idea of period of changing education. It means it is changing since you were a student. You can use time expression in present perfect tense.