As a teacher (high school level) it was really really tough having an integrated classroom I had six groups of thirty kids move through my room each day (that is 180 kids I taught everyday).
I had kids who were autistic that barely spoke, autistic kids who acted out physically/sometimes violently (I was given an emergency number to call, that aide covered three high schools), autistic kids who you would never know they were on the spectrum until you got their paperwork, kids with physical disabilities, a child with Tourette's, extreme ADHD/ADD (medicated and non-medicated, the special ed kids who just needed more time on projects or not taking off for spelling, etc, typical kids who were below average, but didn't qualify for special education, totally typical kids, above average kids but not gifted, gifted & talented, and those that pushed the level of G&T (they went to Mensa meetings). I never had an actual aide that stayed with any of the children ages (14-18). The majority of the boys were bigger than me.
Now plan lessons that meet the needs of all those students and teach them, find a way to adequately and fairly grade each of those lessons, wash, rinse, repeat. Oh and make sure to keep up with all the paperwork on everyone and specific needs on all the IEPs. And whatever you do don't make a mistake by counting off for grammar or spelling on the wrong child, because their parent instead of contacting you and reminding you of their child's IEP (I had probably close to 30 of them) so you could simply fix the grade...would pull you in front of your administrator and want you dressed down.
I have to say I loved loved loved the kids I taught and tried so hard to keep everything straight for each of them to get the best out of my class and the most of their education. I worked very very hard to give each kid the very best from me.
It was the hardest job I have ever done...the best but the hardest...I loved it, but I came home exhausted every night, I worked 10 to 12 hours days and sometimes weekends too.
I know that it brought the students who struggled up to a higher level of performance...but I know there were times where the advanced/G&T students were held back from what I could give them.
I have pondered this question many times...and I think from a teacher's point of view it is different than a parent's or an administrators's or policy maker's because we are trying to give everyone our very best...and sometimes our very best isn't always good enough for all, and we want it to be, and it makes us feel defeated.