there seems to be a lack of communication here, which makes it difficult to know how much of a failure it is that this particular child cannot read at 6
children develop at different paces and he may simply not have been ready
then again, blaming you doesn't seem very productive
I would make an appointment to see the teacher, explain that you are concerned about him getting left behind and ask what the school is doing to address the problem:
has he got an IEP (individual education plan?)
what are his targets for this term?
how are they going to help him meet them?
do they stream for ability and is he in the appropriate set?
do they have any hints on how you should encourage him at home to make sure the school and you are supporting each other?
btw asking you to read with him at home is not the same as expecting you to teach him to read; it's more like homework- reinforcing what he has learned at school. Getting used to reading in a home environment is central to his learning, so from that point of view the teacher is right. He's not going to learn much if he is left to think that reading is just something you do at school, not something people do in real life.