Behavior, Liam's update we are no closer to a diagnosis

For a long time, I have known Liam isn't quite like other children, his behavior is very erratic not just at home, but at school as well he doesn't like change, he gets very frustrated easily and lashes out, he doesn't Listen, he still has no established friends at school, although a lot of the children like him he isn't really bothered if they're their or not.
Liam has been under the pediatrician for quite sometime, they are thinking that maybe he has ADHD, Autism Or ADD, he has also recently started showing signs of anxiety

This is what has been happening so far,

• August 2014 - Liam has a meeting with the pediatrician she wants assessments from speech and language, hearing tests, and the educational psychologist to see Liam at home and at school.

• October 2014- Liam passes his hearing test, although the test was to put a coin in the box when a beep sounded, Liam proceeded to put the coins in when ever he felt like it. speech and language book an appointment to see Liam for November.

• November 2014 - Liam's appointment is cancelled because there isn't enough speech and language therapists the appointment is re-booked for January in a surgery the other side of the town that we live.    

• December 2014 - Liam sees the educational psychologist at school she only carried out half the assessment required and booked to see us at home but never turned up.

• January 2015 - Dad takes Liam over for his appointment, when he gets there the appointment had been cancelled again.

• January 2015 - A big meeting is called, with all the professionals including myself and Liam's Dad, no decisions are made as the assessments that are required haven't been carried out. It is decided that my self and dad needed to attend a course and Liam was to be refereed back to the educational psychologist and was still to see speech and language.

• February 2015 - Liam See's speech and language and passes his assessment.

• April 2015 - Another appointment with the pediatrician and there is still no further progress to report. Apart from that Liam's behavior has deteriorated at school and he is showing signs of anxiety and is talking a lot about death and bad things happening.

• May 2015 - The Educational psychologist comes out to see Liam at school, and forgets to bring the right assessment tools, we are now still awaiting this and another meeting is being arranged with all the health and educational professionals.

So you see it is a long journey it makes me really cross and frustrated at times nobody seems to want to take responsibility for anything, and this has been going on around three years in total now.
Liam is not learning anything at school as he spends most of his time doing naughty things, almost every week I am being called into the school, and sometimes everyday its really tough for us all. I wish I knew the answers but I don't, I wish I could make him happier but I cant, Liam hates school and I can see him ending up in a different school and to be honest that might be the best thing all round, but for now we are still trying to get a diagnosis and his current school are still trying to manage him, but they're already not coping and are struggling to know what to do next with him even though he already has a one to one support teacher.
I have no idea why things have to take so long the schools just don't seem to have an effective system in place to help children with difficulties its seems to be one long battle after the next.