If you want to go to school, take your children to that school first. Of the three primary schools you mentioned, I think the pipeline bureau primary school is the most difficult to enter. Because the pipeline bureau primary school used to recruit children from insiders of the pipeline bureau. At present, there are also outside students going to school, but the control is quite strict. You can try it first.
If the pipeline bureau primary school can't get in, you can go to the fourth primary school. Now the eighth primary school is building a new teaching building, and all the students have transferred to the fourth primary school. But not in the same building. There is not much difference between the two schools. I wonder if you can bring some money. It is best to know the teachers inside. You take the children with you, because my school needs to evaluate the children and see how their abilities are. Six years old is the first grade. If you attend preschool at the beginning of that school, it will be easier to enter the first grade.