One big advantage I see is the chance to break down the barriers between
people with special needs and "regular" folks.  When special ed. kids
are pulled out and in a "special" class, many people (parents, students,
teachers, admin...) don't understand them and don't try to because they
don't have to.  Having special needs kids in regular ed. affords
everyone a chance to exist together as it is in the real world,
hopefully becoming more compassionate, understanding people in the
process.

Just a 5th grade teacher's perspective....

Linda