Require assistance for comparing multiple columns

Im trying but it gives me the error on the column name, even if i change the column name.

Im sorry, im no programmer therefore i don't understand where im going wrong.

let
Type = Table.TransformColumnTypes(Source,{{"Student district ID", Int64.Type}, {"Student Names", type text}, {"Student names having taken the test", type text}}),
Students = Type[[StudentNumber],[StudentName]],
Merge = Table.NestedJoin(Type, {"Student names having taken the test"}, Students, {"Student Names"}, "Test", JoinKind.LeftOuter),
Expand = Table.ExpandTableColumn(Merge, "Test", {"Student district ID"}, {"Student names having taken the test"})
in
Expand