how many studentsin our school are there in your school?__ the students in our chool__over3housand.

A
1．the number of表示“……的数量”,跟复数名词连用作主语时,中心词是number,谓语动词要用单数.例如：
The number of students in our class is50．我们班学生的数量是50人.
2．a number of表示“许多”,相当于 many,修饰可数名词复数.作主语时,谓语动词用复数.number前可用large,small等修饰,以表示程度.例如：
A number of students are planting trees on the hill．许多学生在小山上植树.
因为是整体概念 所以是is