ことになっている says that a rule, a custom or an arrangement is in force: "you are supposed to", "it is the rule that", "is scheduled to". It follows a verb in the dictionary form, or the ない-form for what is not done.
。
At this school, (students) are expected to wear uniforms.
。
It is the rule that you don't take photos here.
。
Employees are expected to do radio calisthenics every morning.
The 〜ている here is a state that results from a decision. It does not mean "is becoming": the rule was settled earlier and still holds.
Arrangements and schedules
The same form covers a plan someone has already fixed, often not the speaker alone.
、。
I am scheduled to go on a business trip to Tokyo next month.
。
The meeting is supposed to start at 3 o'clock tomorrow.
ことになっている or ことにしている
is a rule you set for yourself, a habit you keep on purpose. ことになっている is a rule set by others: a school, a company, custom.
。
I make it a rule to jog every morning.
A personal habit.
。
Students are expected to submit a report every week.
A rule set by the school.
reports the moment a decision was made; ことになっている describes it as standing.
Lingaku