should kids with special needs be in segrated classes or not?

IMHO, this depends on the nature of the "special needs." Whether to
mainstream a student or provide separate attention should be a
decision that is made on a case-by-case basis. Grouping all "special
needs" children into one category does a disservice to everybody.

I have a daughter now aged 20 who was said to have special needs. 
these were physical only, but we found it difficult to get some
teachers to appreciate this until theu got to know her. In fact she is
exceptional bright and is probably going to get a first class degree
this summer. At 7 one teacher said she couldn't read at all, despite
the fact that in her previous class she had been assessed as having a
reading age of 14 and a comprehension level beyond that. I agree with
the previous writer about individual cases. This may also vary during
the educational lifetime of a child. My nephew is totally deaf. He
went to a special school and did well. He is now a computer engineer,
but makes little attempt to integrate into mainstream society. Another
child with the same degree of difficulty did well in a mainstream
school and some are even unaware that she is deaf until they are told.
The main reason I think that special schools have some advantage is
that classes tend to be smaller. Otherwise I would vote for
integgration wherever possible.