If the medication is not working, it may be that your daughter doesn't have ADHD at all. There are many conditions that mimic ADHD that need to be ruled out. Since ADHD often coexists with learning disabilities, you have to make sure you rule out LD. If your daughter has a learning disability that makes school hard for her, she may do things that get her sent out of class, helping her to escape a difficult and stressful situation.
For example, if she feels she can't compete with the other kids, she may do silly or annoying things to avoid having to do embarrassing ones - such as read or write in front of them. She may be trying to protect her flawed self-image, but in doing so she risks turning off her classmates and sibling. The classroom teacher has to understand these sometimes subtle manifestations of LD and ADHD. The classroom has to be organized, with a predictable schedule. A majority of the tasks your daughter is asked to do must be within her range of competence.
It's important that your daughter have a thorough evaluation by a team of professionals familiar with ADHD and other conditions that cause behaviors that look like or are associated with ADHD. Children with allergies or endocrine problems may also display behaviors that are mistaken for ADHD. Kids with hearing problems are often hyperactive (seeking visual input to augment poor hearing), or appear nosy or even paranoid (trying to figure out what was said), or frustrated (because they can't process all the verbal information that's flying around the classroom, both during academic or social times).
The same can be said of children with a serious form of learning disability called Central Auditory Processing Disorder. When children have this condition, they hear fine, but can't process auditory information. This condition is often missed by learning disabilities specialists. A pediatric audiologist is the professional who is trained and qualified to assess this condition. Kids with CAPD often seem "spacey" or inattentive, since the words are essentially going right through their brain without being processed. These children may have problems following directions or understanding lectures or social interactions. If they don't "get" jokes, they may say silly things to try to fit in, or act out in ways to get attention.
Kids who are depressed sometimes display hyperactive behavior. Most professionals think that kids do this unconsciously to make their lives more interesting and exciting to "ward off" the depressed thoughts or feelings. The important thing is to make sure that you have the right diagnosis, and then make sure that you and the teachers are using the most appropriate treatment.