Quick lesson: Modeling companies are like car companies, only the product they put out ends up in the back seat instead of coming with a back seat. But seriously, should you want to get into modeling, yes, modeling companies can help you get a foot in the door, but they have to be highly motivated. The problem is that there are few that can get you really good work, and the rest will only be able to get you crappy or mediocre work, if they get you any at all.
You almost would do better to get together with some other friends who are also models, and or designers, and create your own line of clothing that you can model yourself. Modeling companies will only take you so far, if they take you anywhere, but being an entrepreneur will give you something that will last your whole lifetime that no one can take away from you. You don't have to completely write off modeling companies, just don't completely rely on them as if they are going to hand you a career on a silver platter.
The one thing that you can count on in dealing with modeling companies is that you will learn, and you will get experience. They will get around to sending you out on auditions, and you may get lucky and meet someone in the company that takes a liking to you and makes an effort to impart some of their wisdom to you. Remember, though, modeling companies aside, the most important variable in the picture is you.