I think that it is fair to expect that those tasked with educating our youngest citizens would be reasonably competent in the subjects they are teaching. It is a difficult area but as you know I tend to the Finnish view which is to professionalise teachers highly and then allow them autonomy in deciding what and how to teach. This is only achievable if you do what they do - allow only their brightest graduates to become teachers and give them a thorough (Masters level) grounding in all the necessary skills and pedagogical knowledge-base required. This takes time and a lot of money and both of these things are off-limits in England - the plan is to train teachers 'on the job' and as quickly and cheaply as possible. We then attempt to 'compensate' for lack of teacher professionalism with a highly prescriptive curriculum and a punitive inspection regime designed to 'weed out' 'incompetent' teachers. In my view this is a circle which will never be squared.
[In Finland]The intention is to empower teachers and enable them to influence the direction and development of educational reform, whereas in England the government is characterized as riding roughshod over the teaching profession through a kind of ‘democratic totalitarianism’ in which change is achieved by assertion and coercion (Richards, 1999). The new professionalism envisaged by the English government requires total compliance to centrist demands. The imposition of nationally prescribed curricula, and more recently pedagogy, together with external accountability mechanisms linked to marketization, have been viewed by many commentators as reducing teachers to technicians and signalling an erosion of teacher professionalism
From A comparative analysis of primary teacher professionalism in England and Finland, Webb et al, 2004
If teachers were all of high enough calibre to design and deliver a broad curriculum confidently and competently, and if there were not high-stakes tests at every step of the way, but only a school-leavers' exam as in most countries, I think the demand for tuition from anxious parents, teachers and children would be much reduced. As things stand, with increasingly constraining measurements determining access to 'the next stage' from the earliest years of primary school, a demand-led market in buying advantage is bound to grow. IMHO