Wandering hen

Hi - We have just started keeping 2 chickens and so far we are having great success.  Three weeks in and my 5 year old still gets up every morning at 6am to feed, water and "let the hens out".  2 eggs a day and I think 2 very happy chickens.  The only problem is our local school (about 1/4 mile away) has 5 hens and a rooster, which we can hear from our house.  Yesterday our hens were more vocal than normal and after being out of the run (we do this daily) and in the garden for about 5 hours one went missing.  Of the two she is by far the most inquisitive and definitely the leader.  We have a walled garden with one gate that has a very small gap at the bottom - too small for a fox so I presumed too small for a chicken.  There is a small Wendy house in the garden which he cat jumps onto the roof and gets over the wall that way.  The bottom of the sloping roof is about 3ft off the ground. There were no feathers in the garden so I ruled out predators.    Fortunately after some searching we found her at the school with the other hens.  My question is (perhaps silly), did she fly over the wall, or would she have squeezed under the gate, the gap is 3ins and the hens are 18 weeks old so I presume almost fully grown.  The other question is, is this something she will continue to do and if it is, any suggestions?  We really don't want to keep them in the run all day and if she is desperate to be with the rooster and other hens then I may have to let them go.  It would break my daughters heart to loose them either this way or to a fox on its way to join its new friends.  Any suggestions greatly appreciated.

Chris

She might just have followed the cat!
Seriously though might be an idea to clip one wing if she is flying, and yes a chicken can squeeze through a very small gap indeed!

Kate's right - a fox only needs a gap as big as his head (about 4") and he's through!
but he can also burrow, so if it's not 4" when he started, it would be when he finished... (unless it's on concrete, of course....)

I've got a kids' storybook in my shop called Queenie the Bantam that features a hen who wanders over to a family's house from her own farm.
Never thought it would be based on a true story! 

Love the idea that a school has chickens! Could it be the lure of the cockerel as he is so close, they can be very persuasive mine even tells my girls what to eat! Def need to clips their wings or all may follow other to the school! In my experience cats generally leave grown up chickens alone they may watch or prowl round housing but think they are just curious. Just scare him off (in a nice way) if you are worried and he will learn to leave them alone.