Unless the child is severely disabled, I think granting them access to more regular education spaces will help them develop more hope and positive thinking, Plus that way the student/s feel/s accepted. Plus not all disabilities really prevent the child from learning, By lumping someone let's say with OCD to someone with schizophrenia is doing a bad impression on their will.
For one, Obviously many disabled students need a certain amount of specialized treatment, Counselors or certified helpers (besides a teacher who probably doesn't have the experience or training to deal or effectively help disabled students) and depending on the type of illness or disability those students have, It can disrupt class sessions which impedes on the focus of other students ( I have first hand experience in seeing everyone in classrooms distracted from what the teacher is teaching and just seeing what an autistic (professionally diagnosed) student would do since he would sometimes act irrationally and shout or mock the teacher). Also depending on what kinds of students with different types of disabilities are moved into regular classes as some form of desegregation, The material that the teachers have to help the students understand might me very difficult or they would be forced to take time out the class to teach different and specialized material to two groups of student in the same classroom, Which would obviously be a mess and classes (especially into middle and high school) are short and many in number, Usually 6 classes per day in middle school and 8 in high school. How will any of the parties involved, Regular students and/or student with highly treatable/manageable disabilities, Moderately or severely disabled students, And educational staff, Deal with all of these complications on top of the other problems plaguing public education systems in many countries. It all just doesn't add up, Unless we keep this kind of segregation in order to deliver quality education to all students in accordance to how they learn and what types of disabilities impede them. Just in case anyone speculates anything about my feelings toward segregation in the public education systems, I don't believe public education (or any certified educational systems such as charter or private schools) should discriminate students based on race, Color, Or creed.
Abolishing it means students with special needs mean they will fall behind in regular school cause they aren't in the normal teaching level like other students and it will put a lot of pressure and most teachers are more likely to treat them with disrespect because they have special needs and don't have the normal teaching level with other students.