I was in a gifted and talented program in Years 5 and 6 (it was a composite class). We had to take a special exam in Year 4 to qualify for the class, and then I transferred schools to be part of the class. We were integrated in the school with everything except the classes. They were the two best years of my schooling, even though I still didn't quite fit in (I was expecting a class full of nerds and I was way nerdier than most other kids... in fact, about four of us were later separated from the others, put in a special table, and given extension work). I flourished because I felt I was finally stimulated and the teacher had been teaching the class for a long time, so she understood the needs of the kids whom she was teaching. At my old school, the teachers had despaired about what to do with me other than get me to help the other students, so I was put in Year 6 math lessons and reading lessons in Year 3, and then I sat around rather bored the rest of the time. The extreme boredom was grating (I ended up depressed about feeling 'caged' in high school... I don't want to brag, since it's more because the classes were aimed at the million struggling students and I was just left to my own devices because anyone who was remotely competent was a genius at that school -_-) and I felt that I was underfulfilling my potential, which is why I resorted to self-teaching and bringing books to school.
The good thing about the gifted class is that it was more or less voluntary; I suppose parents could bully their children into taking the exam and joining, but nobody could really complain they were isolated and made a big deal of if that didn't happen. The class was mostly full of people from that school for some reason (I don't know why, maybe students from other schools didn't apply because they'd have to transfer?), so nobody was really separated from their friends, and those that were, well, that can happen in primary school anyway, when everyone gets put in different classes; they still met up during breaks and sport and such. So socially I didn't feel like there was a real problem for anyone (I just sucked socially, but I had a friend outside the class as well). My primary educational concern was challenging myself anyway.
I attended some pretty crappy rural public schools, underfunded, breaking down, etc. Plus I don't know what it is with this town but most of the kids were apathetic (I know that is normal in school but there is a pervasive apathy in my town to everything) and struggled with everything. My English teacher in high school basically told me there wasn't anything she could do for me because I was the odd one out in a class full of students of low literacy and no interest. She said it bothered her that there was a child who actively wanted to learn and push the limits of the curriculum, but because of medical problems (AND EXTREME BOREDOM... boredom is not conducive to getting your work done unless there's an incentive like 'finish all this up and we'll start giving you more interesting work') was hardly getting my normal work done so extension work was out of the question, even if it wasn't such a huge drain on her, and there was nothing else she could do. In the end I was enrolled in university in early-entry English classes. I hated studying in English, later dropped out of high school because I was bullied constantly and was sick of transferring, and transferred to Computer Science.
But yeah. If you're in a class full of kids who can barely string a few sentences together and you can, well, just be grateful you're literate, 'cause you ain't getting much more, was basically what I was told. =/
Regarding class sizes: the gifted class had 30 children, which I personally thought was way too many, and I honestly believe the teacher thought so too. However most of us were pretty competent and used to being independent, so the class size didn't have such an impact on our learning as it had had on the normal classes I'd been in before (and in high school). Speaking of independence, on my report cards the teachers always wrote that they'd wish I'd ask for help more, but I always thought that was rubbish because I didn't need help with the work and they were always so busy with the students that did need help that I'd be sitting there for a long while if I wanted any. :|
At my school, we had a separate Special Ed. program. I don't know much about it except the students weren't separated from the rest of the children during breaks because I had a friend in that class. I was a special needs child because of my neurological and physical problems, so on excursions, they'd be encouraged to go and I tended to get roomed with them because nobody wanted to room with me and my friends were all in other grades, and also so the teachers could 'keep an eye on me'. During things like sports, they'd play with us too, and the ones who needed an aide were allocated one, although the problem with that is it's hard to fund aides for each special needs person. I was fortunate enough to have an aide during my major school trip in Year 10 (seventeen days).
Because I was a special needs student and struggled with a lot of things like organising myself, holding a pencil right, keeping track of my belongings, dressing myself correctly etc. (though I've improved massively since then and function fine in these things except the pencil... in fact I'm a good deal more organised than a lot of people I know), some teachers made certain assumptions about my capabilities. They were wrong. It was frustrating because I needed help in a lot of practical things, like life skills and getting around, but oftentimes I was denied it because I was seen as too high-functioning (they told my mom a lot I was 'so smart' that I didn't need it).
By the way, I skipped a year, and since I am born late in the school year, I was 1-2 years younger than everyone else in my class. I was extremely emotionally immature so they refused to accelerate me further because of my social difficulties. I was always bothered by this but I guess they had a point, since I was fine with adults but struggled with my peers.
tl;dr for the years I was streamed I flourished academically and the rest of the time I was miserable. I often suffered from lack of individualised attention and consideration (as a special needs student on 'both ends of the spectrum' as I was described by one teacher), but a lot of students do. The problem is you can't magic up expert personnel and pay them at schools like these.
