Technically a student with a 504 plan is in special education, however, the type of intensity and regulations are not quite the same as a student with an IEP. In order to see if a child qualifies for more intensive services or different kinds of services the parent should ask in writing for the special education multi-disciplinary team in the child's school to convene.
Remember, parent(s) are an essential person on the multi-disciplinary special education team. Together all people involved should be able to determine what is the best education.
The National Association of School Psychologists has an excellent resource section on their website to answer specific questions regarding the differences between 504 and IEP plans. Their website is listed below.
I hope there is some information in the above resources that answers your question, or that one of the JustAsk community participants with expertise in the area of special education will chime in with more insights for you. Good luck!
Becoming an Effective Advocate means knowing what to do, how to do it, and what your rights are. There is a great book (its published through the California Dept of Education) on everything you need to know regarding Special Education. You are most likely from a different state - but you can order the book for FREE - then see if the laws match to those in your state.