Meanwhile we are struggling to teach her basic fractions.
In switching from private to public in California schools, I had a similar experience. Grade 3 was private, grade 4 public. There was little learning happening in grade 4, but my grade 5 teacher at a public school was one of the best influences in my life.
I think individual attention is the single biggest factor. An experienced and observant teacher will find something in a pupil to drive their interest and enthusiasm. If one teacher has 40 kids to teach, that amount of attention is simply not possible.
I got poor grades when the homework started kicking in. I had a little bit of homework in 5th grade. 6th grade I had a few hours per night. In 8th grade, they put me into regular classes and I had zero homework simply because they were so much easier. I was bored all day, but made great grades. I made Ok grades the next year or two, depending on the class. my sophmore year, we moved again. This school had a more balanced gifted program, and my grades stayed up.
Now, I realize I have my own sort of issues with some of this stuff and maybe others word differently: I have a lot of symptoms of mild dyslexia, which would have been easily overlooked in the 80's and 90's (I moved countries as an adult, learned a second language, and made friends with a psychologist with a dyslexic brother. She spotted it with my spelling problems, but I've not been tested). But the point more is that 8 year olds, even intelligent ones, are still 8-year olds and often have the maturity of 8-year olds. 14 year olds still have a normal 14-year old's hormones.
I went to a private school for K-3 so was way ahead of public school by at least 2 grades, and was bored 4-7. Oh and then my parents wouldn’t allow me to participate in grade skips or an internship at IBM Research Bernal Road. fml. I had the same cookie-cutter education as everyone else.
https://www.cde.ca.gov/sp/gt