I can offer both sides of the story here, as my dd recently returned to school after 9 months of HE.
I took her out of an appalling school last December. She has ASD and was totally unsupported in school. Eventually, she reached the stage of self-harm and wanting to die.
I spent the best part of 3 years practically begging the school to help and in the end I removed her to save her life -literally.
Immediately, I saw a dramatic transformation in her and she started to thrive.
The enforced socialisation other posters think is essential only served to add to dd's stress;
being around lots of people for huge chunks of time is something she finds incredibly difficult.
I have another dd who is incredibly sociable and who loves being around her friends. She is in reception and doing really well. It therefore wouldn't occur to me to HE her (unless she was unhappy at school, of course).
So in one family, we have two completely different children and I would ask that people don't apply a blanket viewpoint to socialisation at school. It simply doesn't follow that it is best for all children to follow the same path.
We found another school some distance away, which is tiny and has a real 'family feel' and dd reached a point where she was ready to give it another try. Her ASD makes her feel very 'different' and she is desperate to fit in. Unfortunately, HE did make her feel different - she got a lot of upsetting comments from children at her old school. We knew we had to give school another try so that dd could have the opportunity to experience a good school environment and see how she faired.
So, she started there in September. The school is incredibly supportive and I couldn't be happier with them.
However, the socialisation issue is again becoming an issue. Sensory difficulties mean that the demands of being around a group of children for 6 hours a day leaves her drained and stressed. Once again, she is starting to fray at the edges.
We are thinking that perhaps flexi-schooling will be the answer for her, but it is so difficult to balance all of her needs.
So please don't assume that HE is a straightforward choice in every case, or that all HEdders have the same opinions and views.
I have seen great HEdders (hello, Streakybacon!) and some not so great. That also applies to none HEdding parents, though.
Children are individuals- as are parents. I didn't know anything about HE prior to doing it myself but the research I did completely opened my eyes to the benefits.