I attended two different Friends Schools up until 6th grade.
I always wished I could have gone back since it was much more free, child-directed, interesting, smaller classes, I did better in school than I ever did in public school. Much less peer pressure, etc. Of course, a lot of that could have to do with the onset of puberty too. I think everyone has a tough time in "middle school" no matter what the school. I don't rememer getting grades, but we did get "report cards" where the teacher would comment on our progress, etc.
In general I remember only good things. Caring teachers, interesting topics, cool field trips!

Edited to add that I remember "meeting" to be intensely boring. I don't know if this is a regular thing in all quaker schools, but we had a short silent meeting (prayer time) each morning before class - like 10 min, then once per week we had a 45 min with the whole school. It was tough to sit still & quiet for that long of time as a young child. But I suppose it is good to teach patience & introspection & peace.

FWIW my parents switched us to public because they were able financially to buy a house in a much nicer town with "excellent" public schools - so they made that choice instead of continuing to pay for private (with a long commute to/fro) while living in a less than ideal town.