Problems at School

This morning, we went to talk with Z's and J's teachers. They said that they think our two sons are too immature to move on to the next grade level, mostly because of their age. Z is seven years old while all his classmates have already turned eight. He won't turn eight until the beginning of the next school year. The same for J. He is six and will not turn seven until this summer when his classmates are already seven.

Each teacher said they feel it would be beneficial to my boys for them to repeat their grade to allow them to mature more. Their ability to do the work is not the problem. Other kids are not doing as well, but will be passed on because they appear to be more mature.

Is that right? Is perceived lack of maturity a big enough stumbling block even though they are able to do the work? Would holding them back a year make them feel bad about themselves...like they failed? I don't now. I am not a child psychologist. I just want what is best for my kids.

Is there anything we can do as parents to help them be more mature or are we unknowingly doing things to prevent them from maturing?

I wish I know where to get some good advice, I feel like the teachers are almost giving up on them.