Comparing things like this between countries is not straightforward. For example, Australia spends $14.1k per student while New Zealand spends $8.6k. That's about 5.2% of GDP for both countries. From those numbers, would we conclude that Australia is overpaying, or New Zealand is underpaying, or that the two countries are comparable?
https://worldpopulationreview.com/country-rankings/education-spending-by-country
I think that goes to my point about simple comparisons being difficult. Norway has a high GDP relative to its size, so 4% might be more than enough for their situation. You also have to account for things like the labor cost of teachers, which varies by country.