I think, for those focusing on the legal aspect, it is worth thinking about the circumstances in which schools may end up not matching the provision in an EHCP to the letter.
It starts with recruitment. For a September start in Reception, a head will review who is currently available in the school. It is likely - given the current vacancy levels and TAs leaving for better paid work in retail or care - that this will need to be a new recruit, as any TAs staying on into the new school year will already be legally attached to other children. If nobody who fits the precise description laid down in the EHCP applies, does the head employ someone who is less qualified or do they leave the position vacant?
Then term starts. As well as the child with already diagnosed needs and an EHCP, 3 or 4 other children start with levels of need that will eventually merit an EHCP but one has not yet applied for. One is a flight risk. Two are violent when upset. One is a serious safeguarding concern. Yes, the employed TA should only be working with their 1:1, but in an overall environment of under-staffing, prevention of physical harm to others remains a priority. The 1:1 TA works with the teacher to take action to prevent that harm and then escorts a violent child to the Head.
Then you have breaks and absences. The 1:1 TA themselves needs appropriate breaks every day. They may be ill. They may leave. They may need to cover eg break duties if there are not sufficient other adults in the school to otherwise supervise children outside while allowing teaching staff a toilet break. The school - and this has often happened over the last few years - may simply not have enough adults on site to maintain all classes open with an adult in front of them AND all 1:1 TAs in place. There are no supply teachers available, even if there was money to pay fir them. Faced with a choice of closing classes or using a 1:1 TA as a ‘body’ in front of a class to prevent this while meaning the EHCP children may be 2:1 OR supervised by a totally unqualified adult, heads may reluctantly decide that not closing classes has to be a priority.
I won’t detail all the other scenarios in which, despite the legal position, a 1:1 TA may not always be exactly the right person nor working 1:1 with their allocated child - first aid emergencies, behaviour emergencies etc etc. In a world where every very high needs child has an EHCP and support in a timely manner from an easily-available pool of resource, this shouldn’t happen. In a world where, for any number of reasons, very high needs children enter school with their needs undiagnosed; where 80% of schools will be unable to balance their books next year leading to significant staffing cuts; and where TAs are leaving in droves, it may happen. Not because heads want to break the law, but because sometimes they have little option.