Jamie Martin, Assistive Technology Consultant for Students and Adults with Dyslexia
Lisa Friedman has offered some great suggestions that may help your son's confidence in school. In addition to her guidance, I would strongly suggest that you get him started on using assistive technology to ensure that he has equal access to the class materials.
Bookshare and Learning Ally are great sources for accessible texts and audiobooks. In addition, text-to-speech technology can help him read any material that is on a computer or mobile device. If he has difficulty with reading comprehension, electronic graphic organizers may help him to visualize the content he is learning about, leading to greater understanding.
Hopefully, having a better handle on his readings will give him the confidence to participate more in class discussions!