I was wondering if the cost is right for this trip; its a high school trip
it includes, flight ticket, transportation, 5 day hotel, museum tours, night tours
it is an international flight
It does sound a little expensive at first sight but do not forget part of the cost is to cover everything for the supervisors (teachers) going with you. Usually they pay nothing on school trips.
If there is one adult for 5 children then 20% of the cost will be to cover their expenses.
You do not say where you are starting off from because that effects the flight cost. The star rating of the hotel can make a lot of difference too.