How about hearing my experience as I am still in school?
I personally feel that in a single-gender school ,
I admit that problems arise in attitude and related issues, as most single-gender schools , as i feel ( which I am in one ) are more academically inclined.
As such, they have little experience communicating with the opposite gender or simply being extremely( boyish / girlish ), which may cause communication problems in the future.
For example, in an all boys school, most tend to care less about their body language, as everyone is a boy , thus displays it in public after 4 years of education in one.
In an all girl school, they may stick closer to their girl friends than boys and hence, the reason for the well known repulsion ( girls all sitting on left side of room, boys on right) .
Technically, the biggest problem with single-gender schools would be how they present themselves after years of education , thus their attitude they display , friends they make along the way.
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In a mixed school, which I feel are just as good as single-gender schools in academics as long as your child works hard enough , can provide a more rounded 'education' in terms of morals.
However, the risk will be at BG relationships when they are young , or falling into a the wrong company , as such affecting their results...
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Therefore, i would agree with computerkid on selection based on your child's talents..
I would strongly recommend to follow that template if your mind is still not made up.
For me, my parents let me have a free choice of whatever I wanted, I had my go at it, and I have not regretted it since then.