How much is band g funding worth on a special educational needs statement?

my son has a statement of special educational needs and gets a band g funding. what we want to know is how much is this worth as we are looking at some special schools and wondered how much his funding would cover the cost of the school.also we are going to a tribunal soon as his statement names a school that's is a behaviour bse school and he needs a school for autistic asd if they do not change their minds what right do we have as there is no way me and my husband want him to go to the bse behaviour school.thanks for any help