Most people whom I've come across that claim they're dsylexic have never actually been tested yet use it as an excuse.
It all stems from the namby-pamby education system in this country where in schools you can't call a stupid person stupid, a lazy person lazy, there has to be some sort of neurological disorder.
It's the same with ADD/ADHD etc. Whilst I don't doubt that in SOME cases it's valid, MANY of them are simply down to bad behaviour, made worse by the parents latching on to these disorders instead of facing the real issue, the lack of parenting skills & discipline.
You can normally spot the genuine cases of these disorders because they're the ones that strive to succeed despite them. Point in case, a member of my year in secondary school was tested and found to be dsylexic. She worked hard and ended up doing law at Oxford.