Absolutely not!
Certainly if you are tall enough and intend to be doing runway work - it is helpful to take a workshop to learn how to work the catwalk - but you don't need to attend a so-called "modeling school."
Do keep in mind that a commercial model needs to be able to act. Commercial modeling IS acting. Acting lessons or workshops can be very helpful in teaching you how to express emotions and portray characters in front of the camera.
In many cities the top casting agencies run excellent acting workshops. Also be sure to check colleges with theatre programs. They often run summer workshops that are particularly great for children.
