I'm researching the situation with schools in Catalonia, Spain and am trying to understand if there is such thing as an affordable private school for children in terms of fees? Anything in the range <= 400-500 EUR per month for tuition? Or are they mostly expensive and even more expensive? I know I can check out lists and websites of schools themselves, but it is a bit difficult as there are multiple fees involved and it is not always clear to assess the full cost of education. I should admit though that, unlike with public schools, there are lots of lists of private schools in the internet which is somewhat helpful.
Private schools in Spain may have public funding, which covers part of the tuition fees. This is called a "colegio concertado", and you can expect to pay around 350€/mo. The catch is that those schools are heavily oversubscribed, so I wouldn't count on that.
Other than that, a fully private school would probaby cost you upwards of 700€/mo.
This are rough figures based on personal experience in the Madrid and Barcelona areas; there will be some variation based on locality, but not much.