OK, found this explanation for example from
Tampere
Tampere is divided into geographical catchment areas in accordance with which pupils are assigned to schools. The catchment areas have been approved by the Committee on Day Care and Education.
The catchment area is defined by the pupil’s home address. When enrolling, the pupil can express his or her request on the choice of school inside the catchment area. The City assigns a school for each pupil within his or her catchment area.
Pupils can choose another school if a certain subject or focus area is not provided in the school assigned to the pupil. A change of school is also possible on other grounds if there are places available in that school.
Maximum class sizes have been confirmed for each school in grades 7-9, and have also been confirmed in grades 1-6- for teaching groups in comprehensive school. Teaching groups for different subjects are formed on the basis of the total number of pupils in the school and the capacity of classrooms.
Pupils in grades 1-6 and 7-9 who are resident in Tampere have priority for
a study place in a school assigned by the City. If there are places available in the school, even pupils outside the catchment area can be enrolled in that school.
Pupils resident in Tampere have priority in obtaining a place in city-maintained schools, but pupils residing in other municipalities can also apply to schools in Tampere. For pupils residing in other municipalities, decisions on admission to a school are made by the Head of Education.
So basically a school is obliged to take pupils from its catchment area - then what that is depends, say for special education it can be the whole city. There is a bit different thing if you have special needs school, or foreign language education etc. Counties provide free school trips, but they will usually not pay if the child is going to a "non-assigned" school like across the county border except if they approve the reason. Some schools, like the ones having basic education in English can have tests for the language ability of the kids before they enter.
High schools then have a bit of a different system. They usually put the applications in a row by average. So some high schools tend to be a bit more cream-gatherers than others.
What you must understand is that in Finland there is all the time the official to try and have no "better" or "worse" schools - they are very reluctant to publish any statistics on how pupils in different schools perform to avoid parents competing for better schools - or atleast there is not such high competition as I understand is in Japan? Of course there is the thing about location, size, options available etc. bigger schools have more choises for extra tutoring for example, but then again in smaller schools there might be more individual attention. It all depends a bit.
There are some schools with some 'better' reputation but it is all still very democratic. So our system allows one "competition crazy" parent wanting their child into the "right" school once in a while. This system applied to Japan I think would be disasterous, as all the parents would be "competition crazy" except one. Like as in Finland getting into an university is not easy, but not getting in is not a disaster either, and getting into the university cannot be predestined if you went to what kindergarten or what school.
So I think there is a cultural aspect of the competitiveness to consider in evaluating the two systems, as you are asking what do you do when there is a conflict... there are not so many conflicts
