So my daughter was diagnosed with autism at 4.5. We knew when she was 2. She is also hyperlexic so she could read fluently before she started preschool. She is very ahead academically and behind in her social and emotional skills.
At preschool, which she attended for half days, she spent most of the time hiding in a corner or under a table with ear defenders on, or else they called me to come and collect her as she was so distressed. She was so unhappy she wasn't eating or sleeping and having meltdowns all the time. When not attending preschool she was a happy child. It was a no brainer for me.
Socialising: we are in close contact with 3 other home ed families who have 5 year olds (and 3 and 8 year olds) and also see family friends with 2, 4 and 5 year olds. When she finished preschool at 4.5 they also assessed her as working at the level of 18-24m for social and emotional skills so her 2yo sister is a very valid playmate. We have regular playdates and trips out. I believe that playdates where she can be supported to develop her 1:1 friendships is the best possible social education for her.
Adults outside of the house: she has 1:1 swimming lessons where she has developed a good relationship with her teacher. She is also on first name terms with 3 members of staff at our local museum, 1 at our library and 2 bus drivers. She greets adult neighbours by name. She also has a diverse set of opinions from family members she is close to who are very different to me!
Reason for home ed: her SEN plays a massive part but I'd always quite liked the idea of home ed.
I'm going to offer her sister the chance to go to preschool at 3 as I believe preschool is a great opportunity for most kids even if it didn't work for DD1. If she likes it and wants to attend school, I'm open to it, although I'd prefer to home educate her too. I will absolutely take their opinions on how they're educated into account. While they're little, my opinion will hold more weight just as I encourage them to eat more vegetables and bathe more often than they'd choose! I feel like school would be a disaster for DD1 at this point but this could change as she gets older, and I certainly wouldn't stop her attending by secondary age if she wanted to.
The LA has assessed the education I am providing as suitable, but also I assess it myself much in the way I assess my parenting: are the girls thriving? If so I'm doing something right, and if not, I'd look to change things up.