The general idea is that the society can afford to foot the bill for education better than it can afford to have people not attain the highest level they could reach.
Yes, we do enjoy our 50-60-70% tax rates here in Europe. Thankfully Sweden recently stopped pissing away the Swedish taxpayers' money by paying for the university education of foreigners.
Yes, we do enjoy our tax rates because we know the benefits (such as the average quality of life) are higher than in other parts of the world (such as USA). Check out the Charter of Fundamental Rights of the European Union.
The general idea is that the society can afford to foot the bill for education better than it can afford to have people not attain the highest level they could reach.