Is your child on a 504 and receiving accommodations of any kind? If so, and if this is not enough, an IEP may be necessary. Basically, a 504 plan is a list of accommodations such as extra time, copy of class notes, teacher check ins to be sure she has her materials, papers and assignments recorded in her planner. An IEP would go a step further and give her accommodations AND related services and specialized instruction. The instruction can run the from instruction about how to manage anxiety (recognize the signs and teach strategies to overcome), to organizational skills, self advocacy, to study skills and academic skills if she needed them. And, as master of none has explained, it often happens during a study hall or academic support period. Here is a link that compares the two: http://www.ldonline.org/article/6086

It is often hard to advocate for a gifted child if she is making adequate (defined by most states as grade level) progress. Here is an article that might give you some resources to overcome this mind set: "How Can I Fight For a Gifted Child?" http://www.wrightslaw.com/blog/?p=1982

If you have neither a 504 or IEP, an evaluation is in order. In your daughter's case, be sure that it includes an assessment of how her depression affects functioning in school. You have two choices: a private evaluation most likely conducted by an independent neuropsychologist or an evaluation by the school. Typically independent evaluations are more comprehensive, diagnostic and unbiased. In my area the costs range from $2500 to $3500, and it is often difficult to get insurance to pay (although with the depression and add, you have a better case than some). School districts only need to "consider" the evaluation and most often will want to do their own testing to determine eligibility for an IEP. They are more apt to accept outside evaluations for a 504.

Given that your daughter is of HS age, it is critical to get an evaluation is she will need accommodations for the SAT or ACT. The college board is more likely to approve accommodations such as extra time if she has had them in place at school for a more than a year.