I've ridden along side the Kawi Ninja 250 many times, some group longer distance day rides with an older middle aged gal. While the bike is a motorcycle and it seems to me to be pretty capable, but isn't a crotch rocket by any meaning of the term. On the other hand, it has enough go to get out of the way when needed and can maintain 75 down a freeway without smoking.
In my opinion, it's a pretty good first bike. But a few rules: the MSF course is primo, and always wear a helmet and skid-protection; but for a kid, don't let it go to his head that any class makes him an expert rider: remind him that after 50,000 miles of assorted riding he'll still be learning ways cars try to hurt him - some are pretty damned imaginitive. After lots of miles on five bikes, they still try to get me, and I've seen them get friends.
And, one last observation: AZ drivers are the WORST I have encountered in all my travels. People drive crazy down here - all the cars doing lane swapping and cutting people off is a motorcyclists worst nightmare.
'66 305 Dream - sold 22,000 miles (purchased used abt 12,000)
'76 550 K - sold 39,000 miles
'78 750 F2 - sold 47,000 miles
'80 750F3 - sold 54,000 miles
'07 ST1300A - 23,000 miles (22,000 in first two years of ownership, back injury has dampened my riding days, no more 800 mile days)
Oh - and I agree 100% with Funner -- learing to ride alongside an experienced rider is the BEST and SAFEST way to learn. Doing it on your own is perilous.
ps: mileage apprx - my brain is fading as I get older.