Our oldest was just diagnosed with ADD, as well. 

We thankfully have some very caring teachers and administrators at his school which is great.   Even the most caring teachers, however, don't always have a full picture of ADD (some do, thankfully), and don't understand that a child may in fact be motivated but his/her brain just can't, for instance, get that homework from Point A (home) to Point B (school).  There is a disconnect for that child.  As the expert noted in her response, a diagnosis hopefully will help.  We are also having the neuropsychologist who assessed our child come in and share the results with our child's teachers, so that they can understand his situation better (and get it from a neutral and expert thrid party!).  Perhaps you can do that, as well, if your school is open to that.

We have just started our child on medication, which seems to be helping, but of course, medication is never the whole answer by any means.  The books suggested in the previous response will be a great help.  We have also really liked Ned Hallowell's books - "Driven to Distraction", "Delivered from Distraction", and especially "Superparenting for ADD."  Dr. Hallowell is a highly regarded psychiatrist (see link to his bio), has ADD himself, as well as two children with ADD.  The latter book has a very positive (but also realistic) take on parenting and has been a great source of encouragement for us. 

http://www.drhallowell.com/centers/clinicians.html

In addition, our neuropsychologist suggested the website www.CHADD.org for additional resources and information.

Lastly, depending on your child's age, there are books for kids on having ADD, such as "The Survival Guide for Kids with ADD or ADHD."  Look this up on Amazon and then browse from there.

It's a long haul but there is so much to love in these kids.  Hang in there!