1 to 1 is one of those anomalies because statements USED TO be measured by the time a child needed support. This was often just based on medical needs, or keeping him/her entertained so the rest of the class could study without interruption.
It was based on what was convenient to teachers.
Now they have worked out that this is not the best way to ensure a child with disabilities can reach their full potential and so children are provided with inclusive education. This essentially does away with 1 to 1 support as by its very nature it is based on the idea that children are taught inclusively in group.
Most of us know that this is the way children like to be taught, they don't like to be separated and work on their own (exceptional cases only). It also happens that inclusive education not only enhances the childrens lives and access to education, it can save a bit of money as children can be taught together. It is a win-win situation, actually a triple win as teaching methods have become much more child focussed in general and this has benefited all children.
OK it's not perfect but it's a heck of a lot better, for everyone, than segregation.