I haven't been diagnosed totally yet myself, but I can tell you what worked for me.

The only way I have found to pay attention is when the class has a textbook to read the textbook while I am listening to the instructor.
For me, it seems to "lock" myself into the classroom and keep me interested enough to be involved. If the subject matter doesn't interest you I don't believe this will work though.

You have to be very carefull though, because you can make an instructor angry if they believe you are ignoring them and reading the texbook.

Good luck