The problem is, it's not always clear who is a kid with SEN and who isn't. DS was on SA for a long time and it wasn't clear before his dx, exactly what his problems were (later dx with ASD).
I'm sure many teachers initially thought it was just down to the family situation or parenting
. There is a frightening number of children with conditions like ASD, ADHD, SPD etc who will fall through the net because the emphasis will now be on pastoral care rather than a different teaching style.
There are also a lot of children who have social problems, come from care etc, but have ADHD and other conditions as well. It's already the case that many of their problems are assumed to be down to their home lives (I've seen lots of children with clear symptoms but undx). Their developmental conditions might never be investigated, especially without a parent to push for a referral.