While I don't condone writing nasty things about children online I can see why.
Nearly every school class in the UK has at least 2 children with special needs. This very often translates into severe behaviour issues eg assault on staff and other pupils, throwing tables and chairs, kicking other pupils, disrupting lessons by wandering around or calling out. Now the idea was that these disabled children would be integrated into mainstream schools with a 1-1 support assistant. Assaults on staff, lack of funds due to government cuts, lack of applicants etc means most teachers do not have anyone full time to support these children. So you have 1 teacher trying to teach 30 children, including 2 who can be violent and disruptive.
I know they would be happier in a special school with smaller groups, and a higher ratio of fully trained staff. I've actually had this conversation with a group of teenagers in a special school who hated mainstream schools as they always felt the 'odd one out' Special school made them feel included and the same as their peers as they all had difficulties. But the council won't fund it unless it's absolutely necessary.
So the teachers are left doing very difficult job with little support. And that's why they moan!!