Blackberries have a neat app called "Blackberry protect". It's actually meant to track your phone and wipe or lock it remotely if it's stolen, but I can see it being useful to "watch" your children on a journey to and from a location and if you find the phone is being "misused" or maybe as a punishment, you can disable the phone remotely when necessaryI wont be waiting until she can afford it as for safety purposes I think she will need one when she starts secondary, depending on what school she goes to she will have a 15 - 45 minute bus journey. Also some nights and especially if she has after school clubs she wont be making these journeys until it is dark.
I got one when I was 10. This badboy
https://911.bg/bigshopbg/pi/si_3794612.jpg
I think it depends on your situation, where you live etc