Is this in an ideal world with no restriction on investment?
No faith schools.
Abolish league tables.
You go to your local school - no more "choice". Every school has the right number of classrooms for the catchment.
Every school has a music room.
Enough books to go round.
Get back to basics and teach reading, writing and arithmetic properly.
Abolish shit poncy subjects like Leisure & Tourism and all that sort of thing.
More options other than GCSE - no point putting non-academic kids through academic exams. A strong economy needs a mix of skills and successive governments of all colours have failed to recongnise this. Also acknowledge the fact that some people go to school to learn and not to prepare for a job.
Streaming in Maths, English, languages and science.
Strict expulsion policies. If a kid makes it clear he doesn't want to be in school, kick him out. Don't waste my child's time sorting out the troublemakers.
More support, value and respect generally for teachers.
Ofsted to be more flexible and get away from the stupid idea that there has to be an "average", which is then used as a stick to beat the below-average. Look at what the teachers are actually doing with the material they have.