What kind of fence has this place got, that a 7 year old can get in like that?
The bottom line is; no-one (be they 7 years old or 17 years old) should be able to gain unauthorised access to any animal park that easily.
I think you'd be very surprised at how many overnight break-ins there are at many zoos, including some of the big ones. If someone wants to get over a fence or a wall, they'll find a way. I wouldn't go blaming the institution for that.