Not debating or stating whether the OP's thoughts may be right or wrong, just throwing some facts into the ring!Neither of my children are christened but go to the local C of E first school, which has a very good reputation, it may be slightly different for your area, because I live in an area of lots of tiny villages and because we also have a different schooling system (1st, middle and high schools) but our school is voluntary aided, which I think gives the school more powers to allocate children the places rather than the LEA, it is very closely tied to the church, one of the governors being the vicar at the church and the church being right next door to the school, all celebrations are held in the church - ie Xmas Nativity, harvest festival, etc. They also have to attend church for holy communion every thursday morning, so it really is not just about better schooling, the religious aspect of the school is really something to consider anyhow if you are not religiously inclined or atheist.
Because of how the system works, with it being voluntary aided, etc we have to specify our reasons for sending our children to the school, but they will always prioritise for children within the catchment area first, and then whether the child has any siblings already in the school, whether there are any social reasons for attending the school, etc - so if your school is similar, you could have your child christened and still miss out on a place, we have to also provide information on the application form as to whether we attend church regularly and if so they also ask for the vicars name and the name of the church so they can check this out, so it may possibly mean having to carry on attending church after the christeneing of the child, having him or her christened may not be enough. As I said neither of mine have been christened but our schools are struggling to survive as numbers are so low, I think this next year the intake is just 8 children, however they are allowed 20! I had never thought of having my children christened, as I wasn't really into it, however, since my Nan died I am thinking of it more and more, not that it would really be relevant for us anymore as we have now moved into the catchment area which guarantees my children a place, more over church attendance.