I am rolling my eyes at the posters who believe they have found the answer to all teaching woes - one curriculum , one set of lesson plans, one set of text books. One size fits all - problems solved.
In reality how is this going to work? Do you think the selective grammar and the struggling comp can really teach the same material in the same way? There are huge differences between one child and another in the same class, let alone differences between schools and different parts of the country? You cannot teach the top sets the same material in the same way as a ALN group. You also need to adjust for things like the time of day - first lesson many are still sleepy, after lunch some are full of sugar and energy, last lesson they don't want to know. You also have to take into account the different learning styles and needs of those in the class. This is even without the minefiels of making adjustments for those who have struggled to even be in school that day, their home situations are so difficult.
On top of that add government interference. One year your subject may be highly valued, the next no one is interested in it and your teaching time is cut in half. New GCSE and A Level exam specs a few years back nearly did for me. Specs were released with no thought given to teaching materials. I virtually wrote the GCSE 'textbook' and did write the A Level one - from scratch - there was simply nothing made available. Three years of my weekends and holidays went into that.
And even if there were set text books - who is going to pay for them? Our school simply did not have the money. But it costs nothing for the teacher to write their own worksheets and powerpoints and use the projector in class. But of course, the real cost comes to the teachers having to do this - time, worry, stress. Plus my own costs, buying refernce books from Amazon to research and prep. Buying my own laptop and software to prep. None of this money is ever reimbursed.