One of the largest debates about the Swedish school system right now is about "private" schools (schools that aren't owned by the government) and the fact that all education is funded by taxes.
So our education here in Sweden is free or rather funded by taxes. There are basically no expenses connected to your education up until university where you're expected to pay for your own course literature and lunch (which is free in both primary and secondary school). However when you're studying at university you are eligible for student benefits and loans so course literature is rarely a big deal. Anyways, the point is that we pour a lot of money into our school system so that everyone gets a chance to study.
So the thing is that since all education is funded by taxes, private schools with private owners are able to fund their establishment on tax money. For most that wouldn't be an issue if it wasn't for the fact that the owners are able to turn the tax money into profit for themselves. So they're basically taking out "excess" money, from the money that the government has given them to fund their schools, and putting it into their own pockets. How do they do it? Well, by cutting down the expenses. Some do it by cutting down the number of teachers they employ, finding loopholes by taking away courses that are expensive materialvise (while still getting funding for those courses), employing teachers without formal competence (i.e. cheaper teachers) and so on. They're essentially compromising the quality of our education in order to make profit.
Some people argue that these schools shouldn't be allowed to exist or that they at least should be forced to reinvest (some of) their profit into the school system. Some argue that no harm has been done since students in private schools tend to get higher grades than students in public schools** or that the profit isn't even that large.
This isn't really about the education system itself but since people see this as something that affects the quality of our education I'd say that it's relevant. But yeah, to summerise, people are upset because tax money disappears.
** These schools might have students with higher grades but they tend to perform the worst when it comes to standardized test. This has led to another debate about the authenticity of their grades and whether the schools just hand out good grades to make their schools look good.