It depends on the building code. There are many design specifications for schools and office buildings, so what you said is very common. It depends on the code.

The 900 you mentioned is a common door, but there is not only one. For example, in a general residence, the door is 1000 and the height is 2 100, while the door of the bedroom is 900 and the height is 2 100, and the door of the bathroom and kitchen is 800.

The school gate should be a small classroom with a height of 2700 1000, otherwise the whole house will not look good.