What does the evidence say about the impact of K-12 class size?

http://www.brookings.edu/research/papers/2011/05/11-class-size-whitehurst-chingos Among the points it makes is that instead of comparing smaller/larger class size as the only options, perhaps the better approach is comparing several different approaches to dealing with the students, comparing the cost and effectiveness of all the various solutions, and investing money in the way that makes the most sense--perhaps a combination of class size and other efforts to improve student outcomes--in terms of overall student results, not just class size per se. Quoting:When school finances are limited, the cost-benefit test any educational policy must pass is not “Does this policy have any positive effect?” but rather “Is this policy the most productive use of these educational dollars?” Assuming even the largest class-size effects, such as the STAR results, class-size mandates must still be considered in the context of alternative uses of tax dollars for education. There is no research from the U.S. that directly compares CSR to specific alternative investments, but one careful analysis of several educational interventions found CSR to be the least cost effective of those studied.

http://oecdeducationtoday.blogspot.com/2012/12/how-does-class-size-vary-around-world.html:Class size, together with students’ instruction time, teachers’ teaching time and teachers’ salaries, is one of the key variables that policy makers use to control spending on education. Between 2000 and 2009, many countries invested additional resources to decrease class size; however, student performance has improved in only a few of them. Apart from optimising public resources, reducing class size to increase student achievement is an approach that has been tried, debated, and analysed for several decades. Some countries like Finland favour smaller class sizes (20 students of fewer) and are among the most successful countries in the PISA study. However, other countries like Korea have much bigger classes (34 students and over) but also feature at the top of the PISA ranking. What other variables than class size may explain the success of countries like Korea? Findings from the OECD Programme for International Student Assessment (PISA) suggest that systems prioritising higher teacher salaries over smaller classes tend to perform better, which confirms research showing that raising teacher quality is a more effective measure to improve student outcomes.Perhaps you could increase class sizes and increase taxes, so you can pay teachers 25% more than currently is the case...

Thank you for the responses. I'd like to reiterate that the question is about the impact of class size. If data exists that is specific to inclusive classrooms in the US that would be ideal. My question is not, "what is the best way maximize educational outcomes given limited financial resources". That's an interesting broader question but it's not the question I'm asking here.

Thank you for the responses. I'd like to reiterate that the question is about the impact of class size. If data exists that is specific to inclusive classrooms in the US that would be ideal. The impact of smaller class sizes is positive (it's almost always a good or neutral thing), variable (not guaranteed & incosistent), and relatively tiny (when present). As three people have said in different ways. The other two links given are to the same page, which is more on target than my link. They address results of smaller class sizes in the US directly:Studies of class size in Texas and Israel also found benefits of smaller classes, although the gains associated with smaller classes were smaller in magnitude than those in the Tennessee STAR study. Other rigorous studies have found mixed effects in California and in other countries, and no effects in Florida and Connecticut. Because the pool of credible studies is small and the individual studies differ in the setting, method, grades, and magnitude of class size variation that is studied, conclusions have to be tentative. But it appears that very large class-size reductions, on the order of magnitude of 7-10 fewer students per class, can have significant long-term effects on student achievement and other meaningful outcomes. These effects seem to be largest when introduced in the earliest grades, and for students from less advantaged family backgrounds. ...

Google will show you a fair amount of evidence that smaller classes are better, but it's not quite as simple as that. Teacher training, teacher effectiveness, amount of students at risk, levels of disabilities within the class, school resources in general...all of these things are factors. An interesting http://opinionator.blogs.nytimes.com/2013/05/04/does-class-size-count/?_php=true&_type=blogs&_r=0 discusses the issue and has some links. I wish there were a simple answer to this. I run a school where we have no more than 8 students to 1 teacher, and our kids all have severe emotional disabilities, and not a whole lot of teaching goes on some days. I've worked in systems with 30 neurotypical, high-achieving kids with 1 teacher and a lot of learning happened. Bear in mind this is a very difficult thing to quantify because so many factors determine what makes a school system "good:" test scores, class size, teacher salary, Title IX money, etc. You can't just say, "Smaller class size is better," because you can't isolate ONLY class size from many other inequal factors.

You'll get plenty of data about class size, smaller is better. One thing you may have an issue with is actual buildings to house the classes. I will propose that if your school district goes to a http://en.wikipedia.org/wiki/Year-round_school_in_the_United_States, that you can have 1/3 as many students in the same building. The school I went to had 9 weeks on/3 weeks off schedule and it was fantastic! The schedules stagger, and classrooms change around, and it's a great way to keep staff in the school employed year round. So, that is a money saving answer to one part of the question. You'll still need to employ more instructors, but you would have needed to do that anyway.