I'm pretty gobsmacked by some of the views on this thread really...
I am a forces wife, although have only been so for three years. DH and I were together for 4 years prior to that. I have 3 DC who are not my DH's and we are expecting a baby together in July.
My oldest DS weekly boards. In September, he will probably board full time as we are moving away. It is entirely his choice and he chose to go to the school he does whilst waiting to see if he had a place at the local Grammar. The only local comp is appalling, so we looked at the boarding school as an alternative. That was his preference. I hate him being away. I am used to it now, after almost three years, but I do miss him a lot, as do my other DC. If it were my choice I would rather he came with us when we moved, but he is in the middle of his GCSE's and aside from that, he loves it at the school and wants to stay there. DS2 would also love to go to the same school, as he hears his DB's stories, but I feel he is too young, aged 10, to make his own decisions about that.
We get CEA, I don't work. I see it as an opportunity for my son to get a good education, it has nothing at all to do with childcare and after all, I have my other DC to look after.
The alternative for us would be to buy our own house and I would live in it with my DC. However, that would mean as well as myself not seeing my DH, neither would my DC and although he is not their Dad, they think an awful lot of him (as he does o them) and have a good relationship with him. They love spending time with him. That option would also be more limiting to us finacially and although we aren't badly off, that would obviously have a negative impact both on my DC and my DH's two DC with his ex wife, whom he obviously contributes to financially. The other aspect of myself and DH living apart would also be that leave was spend between seing us and his DC from his first marriage, whereas this way he can free up more of his leave to see his DC.
Most forces familes where I live do not send their DC to boarding school, of the ones that do, I don't know any under secondary school age.