I only have experience of weekly boarding nursery and pre-school (3 to 7 years old), and though my memory is I did beg my parents every single Sunday evening to not send me back to 'jail' - but I was a very stubborn and not eager to please child - they still managed to convince themselves that things weren't that bad. I 'looked happy' getting off the bus at drop off home. 'I talked about that boy I liked' etc. And obviously if you were spying on me from the outside, I wasn't sitting crying my eyes out all day every day, it's impossible. I must have looked fine most of the time, a normal child getting on with life.
I actually knew as a child that I was extremely miserable there and hated every minute of it and couldn't wait to grow up so that I didn't have to be there any more, but my sister genuinely thought that she sort of enjoyed it.
She is far more sociable and flexible than me, also lived in several different households full-time before nursery, parents, one set of GPs, then another set of GPs, didn't think of anything as home, and she says she didn't miss home or family and didn't mind being part of a commune, she was also far more thick skinned about all the horrible routines and total lack of privacy. However, once she had her own kids, it hit her. My parents sent me away at three?? Somewhere where nobody LOVED me?(actually, there was low level constant child abuse(not sexual) but it's a different story)
You can get education, discipline, social skills, etc outside the family, but you cannot get unconditional love and acceptance elsewhere, and that's a single most important thing for a child growing up, everything else can be caught up on later, but not the love and nurture in early childhood, and 8 is still very very young.
Those who now say - oh, I've sent my kids at 8, they ASKED for it and they grew to love it. Maybe. But wait till they have their own babies, and look at them aged 8, whether they would think - oh, seems like the right time to swap family environment for an institution. It will be a better life for them. See if they think it or if they wonder a bit about their relationship with their Mum and Dad.
OP, it's not an attack on you, you've obviously been somehow brainwashed into thinking that was the best thing for your child. Just listen to your instincts.