Just one addition - unless it is very different where you all live, its not going to be like the new yr 7s are all totally phone aware and having strong views about them. Although quite a few of dd's friends have phones, definitely not all, and in my experience at least half of those that do don't actually ever use them (or like dd's yr 8 friend 'he's got a phone and he plays games on it but he isn't allowed a SIM til he's 13' ).
DD uses DHs old (£10 Alcatel brick) when out and about, and its certainly not a cause of any embarassment, in fact she's probably the one who will actually know how to use it and make the phone call when they need picking up or whatever.
Our DC swear that everyone has a smart phone and then get all hoity when I name some names who turn out not to.
Where we live, everyone has to travel on public transport to secondary and there have been incidents of children having smartphones whipped out of their hands by people jumping off buses and trains. So I told DC Nokia PAYG for the first term and if they feel really comfortable with it and never lose it, then we'll move on to a smart phone at Christmas.
You can get good Nokias online for as little as £5 on a PAYG contract. DS1 is on his second top up since November (spent about £30 in 9 months) and DS2 is still on his original £10, but he has an I-pad and skypes and facetimes people on it, so needs the phone less.
Takver you've just perfectly summed it up. DD1 has always used her phone exactly as it was intended to be used - texting me on school trips to let me know she was going to be back late and keeping me updated on ETA, letting me know when her younger sister was late back from school on a day she was not scheduled for an after school activity, generally keeping me in the loop. She's a very mature 12yo (most of the time) and sees the phone as a communication tool, not a gadget.
I have also given my old iphone 4 to DD1 who will be starting year 7 in September. My contract expired at the end of last month, so I upgraded to an iphone 5 and she has a contract which costs £7.74 per month, so this seemed like the best deal. I do hope that she doesn't attract any muggers though. She didn't really want my old phone but wanted a galaxy ace like lots of her friends, but this was the cheapest option.