To get kids into a state school they will need to be on the padron which you can do at the town hall.
I don't mean to come over all heavy but if you move over in January, won't that be really disruptive to your kids' education? You said in your earlier post that you wanted to wait until your eldest did his GCSEs.
We live on the Costa del Sol and the honest truth is that most expat kids that arrive here at an age where they struggle in the school with no friends in a language they don't understand, they tend to end up as wasters. We see them all the time hanging around the port here in Manilva just drinking beer during the day. These kids are anything from 14 to 18. What on earth is their future going to be???
The Spanish secondary education system does not actually force children to study or do well. Those that want to learn sit at the front and those that don't can site at the back of the class and do whatever they want...or just not bother turning up at all.
We have seen so many expat teenagers struggle here that this subject is a sore point for me. It pains me to see it happening. Parents think that their kids are enjoying life in the sun, out in the open, etc, but the reality is that so many leave school with nothing in a country with the highest unemployment rate in the EU.
It's sad but true.
In terms of things getting better in Spain....we're a long way away from that yet.
eggcup, primary international school is normally around 600 euros per month but secondary tends to be more expensive, between 800 and 1000 per month. That's what we found out when we looked intto it.