If you are an aspiring model you should also submit to casting directors, casting directors work with ALL types of models, "real people". For an aspiring model a print agency might not start asap working with you, without any experience, but I would submit your headshot and comp card to casting directors to get your feet wet.
A good source to find casting directors is THE Call Sheet (it used to be called The Ross Reports), it is a little booklet with listed casting directors, it is put out by backstage. At Bookstores in magazine section.
Here I am talking about The Call Sheet:
Casting director’s book talent for work on commercials, print work, and film and theater work. If you are an aspiring model write to the casting director a short note on what areas you are interested in and submit your headshot and comp card. And include a resume, if you do not have any experience list your skills, any clubs or organizations you are a part of.
A print modeling agency at first, without experience, might be tough to get in the door with, but you could be submitting to other options, casting directors are a good to consider mailing your comp card and headshot to as well.