On your podcast recently you asked Ed Glaeser for his political economy model to explain why schools in cities are so bad. I think it may just be schools in American cities that are bad rather than schools in cities in general, and the political economy reason why is probably local control over schools.
I am familiar with the situation in England, where outcomes are better in large cities. English children on free school meals (usually because their parents are on welfare) have substantially better exam results and are a lot more likely to go to university in large cities than in the rest of the country, while children not on free school meals do about as well as in large cities or slightly better.
That said, schools in large English cities were bad 20-30 years ago – in 2001 educational outcomes in inner London were the worst in England – and the improvement coincided with major policy change. Starting in 1990, school governance reforms in England have nearly eliminated the powers of local authorities over schools. Most schools are now ‘academies’ entirely independent from local authorities, and local authorities have very little discretion in how they manage schools theoretically under their control. On the other hand, in the US local government makes more of the decisions on education than in any other OECD country: 72% of decisions in the US are local, compared to the OECD average of 3%.