Special Needs Adult Child Tax Help

[Mamagraham1]

I have a question I am trying to sort out. I have a 20 year old special needs son who is on SSI and still attending a full time school program.  My first question is because he qualifies as disabled for SSI does that mean that he qualifies as disabled per the IRS definition?  I am unsure whether to check the box for that.  He will be able to work but it will be with support.  This is a really confusing definition.  Any clarification would be great as he will continue to live with us so we will claim him as a dependent.

[Bsch4477]

A person is permanently and totally disabled if both of the following apply. He or she can't engage in any substantial gainful activity because of a physical or mental condition. A physician determines that the disability has lasted or can be expected to last continuously for at least a year or can lead to death.