I have been through these international school during my high school years, it is true that education wasn't the most important part of my education.
Most teachers are frustrated by the board, management, and the students by end of their contract but it was way back when the current population of the high-end class hasn't changed much with spoiled brats living in the highlight of Ulaanbaatar. There are schools like British school of UB, International school, and more are uping their standarts and teaching higher meterials (college-prep Cambridge, ivy league education*)
Education wise, it depends on how much you take and give, there are students who really do want to learn but just maybe that one* student should be left behind.
Living in Ulaanbaatar, you just have to adapt to the weather in winter, living close by you wouldn't have that much of problem commuting but the pricing of commodities are high and during your contract period, you can be comfortable but I am guessing saving money isn't an option.
PS: I never taught, never worked with these people, so good luck if you decide to take the offer.