Welcome @kari_0110,
There are at least 4 solutions.
Often using the search function of the forum (and the Help Center articles) can provide help and examples. See e.g.
As first option https://community.kobotoolbox.org/t/how-to-generate-dynamic-labels-based-on-a-calculation/15791/4.
A 2nd simple option would be to use the IDs as choice names and the countries as labels in the same choice list. ${selectVar} would give the ID (i.e. name of the choice item). An advantage is that you easily get the ID also in the export.
A 3nd option would be to use the first value as a choice_filter for the ID list and a select_one type, read_only (and relevant) and with a calculation to set/select the ID choice.
A 4th option would be to use pulldata (or select_from_file) from an external file instead of the choice list to get school names and IDs.
