Certainly round here (Herts) that is the case. If a child is statemented and the school is named on the statement then you come top of the list when places are allocated. This definitely does not apply to children with SEN without a statement even if they have a specific diagnosis.
DS2 currently at private school. Has had Ed Psych reports, but not statemented (dyslexis/dyspraxia). Would like in a few years to move him to state 6th form which we are not in the catchment area. If I get him statemented will this help?
A statement is not necessary if a child has documented medical needs and you can prove that he/she would be significantly disadvantaged by not being able to attend the school in question. Probably hard to prove with dyspraxia, though, unless the school has a particular dyspraxia programme. My friend's children got in because they have special counselling and the children have emotional needs. Dd got in because she is disabled (but not statemented). You have to provide reams of professional letters of support to get anywhere though.
Our LEA does not statement children with physical disabilities, so they have to make separate allowance for medical needs.
A statement gives you a description of the needs the child has which should be met by the school they attend. The LEA then try very hard to get you to accept the cheapest possible option for that childs minimum needs. When my son left his SN nursery he left with 10 other children. Only THREE of those children were offered any school at all!
When DS1 reached secondary age last year I had to visit three schools - two of which were totally wrong for his needs. I would have had to home school him had he not got the school we wanted. [phew emoticon]