Should a young person take art seriously?

If someone is good in photography, graphic designs, illustrations and stuff in age of 14, is it ok to be with it seriously or just for a hobby?

Practice, practice, practice now. Take your art classes offered at school and when you go to college you can get into an art program if you are still interested. There are many jobs in art that offer job security and above average salaries. For example, you mentioned Graphic Design. Anything, dealing with computers and art will continue to be lucrative as long as you stay up to date on your field. Art Education is great major that will allow you to pretty much get a job in any town and school systems offer great benefits and lots of time off. Illustration is also a lucrative field that will continue to be in high demand. Good luck to you and don't let anyone dissuade you from what you want to do with your life.

it is not ok, he \ she should take care of his \ her study first

Take it seriously NOW and establish in your mind what you think art is. Everyone needs to know what art is and take it seriously, especially if they want to do something creative in life. I want my trade to be filmmaking, so I've doggedly studied the artistic styling of my two favorite directors; Tim Burton and Steven Spielberg. If photography and graphic design is your niche, you need to take it seriously.

Might as well, many geniuses are high school dropouts.
our nation's founding fathers didn't even have a 4th grade education. but didn't they do something great? they were much better leaders then our well educated politicians of today

Well, the best thing to do is not get too much into it if the kid just loves art. Don't force him into any schools if he really doesn't want it. Let him have fun with it, maybe go to an art class to learn and compete with other kids, since competition is the spice of life for some (including me).

The problem when getting into their teen years is that they'd probably lose some interest in it as they pick up other things, and the parents are saddened by all the talent seemingly going to waist. Sometimes it's made worse if the parents get too involved in the kid's hobby, or enjoyment. It all depends on the situation, the attitudes of each, etc...

So, I'd let it be a hobby, take them to a local art class and let them have a little free reign with other kids early on.

There are many avenues of study in Art.
You should concentrate on getting your basic education but pursue the interest in as many forms that are available to you These courses, gallery openings, or club affiliations done in your spare time could eventually lead to a career. Moreover, the art community no matter where you are, is quite small and getting your name known will bring its own opportunities. There is power in showing up!! But getting Fine Arts Degree will make your art more credible