Various forces seem to have converged from different directions to force me to learn something about school improvement, and I, conveniently, have very easy access both to one of the experts and to a practitioner involved in improvement at a particular school. Here are some initial thoughts which may be too obvious for you to bother with. Comments on what I need to learn and how are more than welcome.
If you are charged with improving your school, you will usually be told something like this: our aim is to raise achievement for all students and to address the achievement gap. First thing is just that these are quite different, and conflicting, aims. If everyone’s achievement goes up by the same amount, then the gap remains the same. So if you also are charged with addressing the achievement gap, you’d better figure out strategies for raising the achievement of lower achievers by more than you are raising the achievement of higher achievers. 
How are you going to raise achievement of anyone? In normal industries there are two ways to increase output. Either you increase productivity, or you increase the inputs (in the case of education this is mainly going to come in the form of additional labour). Are you being given extra resources with which to purchase more labour? My guess is that, in the current environment in the US at least, the answer to that is “no”. So, you have to somehow increase productivity, that is increase the effectiveness of the teachers you already have.
So, what increase in achievement are you aiming for? Do you really think that you are going to close the achievement gap? That is, do you really think that you are going to get the lowest achievers in your school achieving at a higher level than the highest achievers currently do? (which is what you have to do if you are going to pursue school improvement at the same time). Think for a moment at the Herculean increase in productivity that would require. Do you really think there is that much slack in the school? Or do you mean, by addressing the achievement gap, something much more modest, like increasing the achievement of the highest achievers by 5% and that of the lowest by 10%? If so, and if you are going to be improving the school, then you still need to find something between 5 and 10% increase in effectiveness.
How are you going to do this?
Nobody denies that schools have lots of inefficiencies in them (or rather, some deny this publicly, but none do privately when pushed—my experience is that when a teacher denies there is any waste in their district, the easiest way to get them to retract is to ask what they did during their last in-service). But some of those inefficiencies are not within your power to eliminate; you cannot fire the worst teachers and principals, for example, or prohibit teachers from attending wasteful district meetings. The constraints are less strict if your district is on board with improvement, and is willing to implement district-wide policies that make sense. But still, you have limited space. Other inefficiencies are just difficult to identify. Mainly, what you want to do is improve the quality of the classroom teaching, and improve the fit between students and teachers (e.g., if you find that some teachers work especially well with middle-level achievers you assign them to classes populated by such children; if you find some work very badly with high achievers you don’t assign them to such classes).
But how are you going to do that? The truth is that while lots of people in the building “know” who the good teachers are, very few people in the building actually know much about what is going on in anyone’s classroom. If that’s not true in your building, then you already have a pretty good school, and while you should try to improve you should also understand that you can’t get much better than pretty good. If it is true, then the way to improve is to find out what is going on in the classrooms so you can improve it. The teachers who are successful should be observed by those who are less so, and should mentor them; the teachers who are especially successful with particular sub-populations should be assigned to them more often than they currently are.
But how are you going to figure out which teachers are more successful? The standard way of doing this is by listening to gossip and following your instinctive emotional reaction to the teacher in question. My guess is that the worst gossip is worth following up, but that otherwise you’ve just got a lot of noise.
You need a common curriculum, well articulated, and common assessments so that you can figure out which students are actually learning from which teachers. Mapping curriculum is a lot of work, and has to be done, in part, by the teachers themselves. Successful mapping is needed for figuring out who is teaching effectively, but it should, also, free up considerable resources. Think of all the time that beginning teachers spend working up curriculums that aren’t so great and that they don’t have confidence in (even when they are great) because they have nothing to check them against except their underdeveloped instincts. With curricular materials and lesson plans already available for them to follow and modify (and in which they can at least have the confidence that their school approves of them) time and energy is freed up for concentrating on teaching students. In a school with these resources some proportion of early career teachers who would otherwise have dropped out in frustration and because they are burned out may not do so – over time you have fewer beginning teachers and more experienced teachers in the building.
Doing all this is a lot of work, takes a lot of time and discussion, and requires capacity that lots of schools don’t have readily to hand. For example, many schools do not have people in them who know how to, and are willing to, run a meeting—design a timed agenda, draw in all stakeholders, facilitate discussion among people who have different experiences and real disagreements. Most people, in my experience, don’t even recognise that this is a skill. (My tip—if you are in a district that is running a school improvement effort, convince UTLA to release its special projects director (scroll down) to train people in all your schools to chair meetings—he’s the best there is).
Judith Little is frequently quoted at length (most recently in Fullan’s The New Meaning of Educational Change) and it’s worth thinking about the reaction to this quote if you handed it out among your staff:
School improvement is most surely and thoroughly achieved when: Teachers engage in frequent, continuous and increasingly concrete and precise talk about teaching practice (as distinct from teacher characteristics and failings, the social lives of teachers, the foibles and failures of students and their families, and the unfortunate demands of society on the school). By such talk, teachers build up a shared language adequate to the complexity of teaching, capable of distinguishing one practice and its virtue from another.
Teachers and administrators frequently observe each other teaching, and provide one another with useful (if potentially frightening) evaluations of their teaching. Only such observations and feedback can provide shared referents for the shared language of teaching, and both demand and provide the precision and concreteness, which makes talk about teaching useful.
Teachers and administrators plan, design, research, evaluate and prepare teaching materials together. The most prescient observations remain academic (“just theory”) without the machinery to act on them. By joint work on materials, teachers and administrators share the considerable burden of development required by long term improvement, confirm their emerging understanding of their approach, and make rising standards for their work attainable by them and by their students. Teachers and administrators teach each other the practice of teaching. (itals in the original, but the bolded part is my doing).
The question isn’t just whether this is going on in your school. The question is, if it is not, how will teachers react to the sentence I have bolded? In plenty of comfortable suburban schools in the US it would be anathema. Some of them, are also going to fear that any move in this direction will, ultimately, be used to evaluate them (and they’re going to be right!). But one way or the other, both improving the school and addressing the achievement gap requires that managers give close scrutiny to the effectiveness of teachers, and requires teachers and administrators to understand that they have to see their own learning about teaching the way they see their students’ learning and even their own learning about every other complex and difficult activity. If you don’t think teachers and administrators should be observing, evaluating, and learning from each other, then you need to think very hard indeed about where improvements are going to come from.
If, of course, you are an administrator or, as is more likely, you’re someone without management authority who has been put “in charge” of running a school improvement initiative, and you are in a school where the above quote will be ill-received, its probably not a good idea to move straight into evaluative mode! But you do need to figure out how to get people to the place where they see mutual observation and learning as worth overcoming their fears for.
Now for the depressing coda. The populations of schools that recognise they need to improve is not constant, but in flux. The amount of control that the school has over student achievement is limited. Out-of-school influences also have an effect. If the demographics are changing, then it is entirely possible that in 3 years time your achievement will be down across the board, and the gap greater, despite the fact that you really have improved, and addressed the gap. For a lot of schools this is very likely indeed right now, because the economic crisis will result in more kids being more disadvantaged, and more at who are quite disadvantaged becoming very disadvantaged. Make sure that you and your staff understand something about the limits of the effects of schooling on achievement, even as you try to improve those effects.
 “The achievement gap” is an unfortunate phrase. Policymakers often mean something quite specific (but counterintuitive) by it – the gap in achievement of some low level of proficiency in certain skills between children from different social and, sometimes, racial backgrounds. But teachers and administrators sometimes take it to mean more or less what it would mean in ordinary English. Since nobody seriously believes that the achievement gap in this sense is eliminable, it is setting people up for failure to talk about “Eliminating” or even “Narrowing” the achievement gap. Some other phrase altogether might be better; a less final one like “prioritizing raising the achievement of the lowest third of achievers”. If anyone can come up with a pithy phrase that captures that I’ll tell my dad to start using it.