Okay, you wanted a home ed perspective and here's mine. I have a learning disabled teen who has always been home educated.
Mainstream school is predicated on the assumption that all kids will be more or less learning the same things at the same age in the same way. If they can't, they will have problems.
In theory teachers can differentiate for kids who are at different levels. In practice, one teacher with dozens of kids in a busy classroom is not going to be able to fully meet the needs of kids with diverse abilities or learning styles, no matter how talented and dedicated the teacher is. It's just a limitation of the mass instruction model. If your child is going to stay in school, you and the school do need to figure out how she compares with the other kids in her class so you and school staff can try to help her get by in the classroom environment.
I absolutely understand why you find that hard to stomach. So would I. It has been brilliant for my home educated special-needs child that she does not have to have her needs constantly formally assessed, because she can get a targeted education without that. She was over ten before she even knew that if she were in the school system, people would consider that there was something wrong with her. Home ed has been the making of her.
On Mumsnet when posters complain about school, I often hear people replying rather snippily, "If you don't like how school does things, home educate." I say to you more kindly, "If you don't like how school does things, home educate." Would that be an option for you? Is that why you posted here?