BE AWARE - The regional test centres ALL differ in how they operate. Spain is like this - get used to it.
I used to work opposite Madrids. The daughter of a Spanish friend has just taken her test there and was given a paper for trafico saying she'd passed - so obviously here the marking procedure is different.
We have lots of small schools near us too. All private and not part of a group. This is how Spain is - full of autonomos. It measn however you need to invest in vehicles.
I cant believe anybody would doubt that fluent Spanish is a prerequisite. Not only would an instructor have to converse with his students - but also with examiners and test centres - plus all sorts of other institutions. These ALL operate in Spanish. This is Spain.
The only english speakers (in general) who'd need an expat instructor will really be those who for some reason lost their licence (dui etc) OR are non-EU. Any EU member can simply swap their licence (use a gestor to ease life by all means) and renewals are a simple process. And kids raised here will be fine with Spanish - unless they've been isolated by their parents.
OH - one BIG point. More and more larger schools are OBLIGATED to offer Bike/Car and HGV training to survive - this from our local school. It means they therefore have to have vehicles available and this (in the case of a truck) is NOT minimal. Our local has car and bike only. Are you HGV and bike certified? - if not you're lower down on the list.
I'd not say Spanish driving is that bad. Ever driven in rural Italy?. Certainly in some areas (Valencia is one) they can demonstrate a remarkable lack of regard for things like traffic lights. But it's way easier to drive here than in the UK now imo. At least here you can concentrate on the road - in the UK I find I'm always looking for speed cameras.
Oh and we drive on the right side of the road here too

