What a curious question you have posed here. Most of the time, questions ask about ideas or topics which should be included (noting relevant information).
An introduction to students with emotional/behavioral disorders, physical disabilities, and sensory impairments should include definitions of each of the terms. Irrelevant information which can be included in this introduction would be statistics on each of the disorders. For the most part, teachers and others involved in the educational world do not necessarily care about the number of students who suffer from a specific disorder. Instead, they are more concerned with what they can do to help students in their own special education program.
Another thing which could be brought up, which is irrelevant, would be if the disorders, disabilities, and impairments are the result of genetics or environment (unless a particular environment acts as a trigger). Sometimes, again, this information fails to help teachers help the students.
One last thing which would irrelevant in an introduction of this kind would be to reference people over the age of twenty-one. Given that Special Education only includes students up to this age, any reference to people outside of this age range would be irrelevant.