Disabled parking bay issue outside school

Hello @MrsMwa.
This sounds like a frustrating situation for all involved. My first thought is that perhaps the school could look at better ways of accommodating all of you? Are there other spaces within which they could allow you (or the other parents) to park? 

I don't think you're wrong to be annoyed, but if you're unsure why the other parents turn up so early, it could turn out your frustration is perhaps directed at the wrong thing. As mentioned by others, they could have a perfectly valid reason for turning up so early. 
A slightly different situation, but my daughter attends an activity once a week and the only way for her to attend is if she knows I'm sat outside in the car, waiting. I don't particularly enjoy sitting in a freezing car park for two and half hours every week and to other people it may seem selfish that I'm occupying a parking spot for so long with no real 'need', but to us, it's a necessity.

We also faced similar challenges juggling the school run after my middle child had surgery some months ago. Despite picking them up early each day, we'd still have to turn up around an hour before to ensure we could access a spot close enough to the school. Unfortunately even then it was hit-and-miss as to whether we'd get anywhere because other parents would face similar challenges and turn up early to ensure they had a space suitable for their needs too. 

I completely share your frustration, but perhaps the solution here is to take some time to speak with the other parents about why they arrive so early, or even explain your situation. You might find they are equally frustrated. I would also keep on at the school and see what provisions or suggestions they can make.

I'm really glad your youngest is sleeping better for you @MrsMwa. I know first-hand how difficult a prolonged lack of sleep can make things and always feel more able to tackle the day when I've managed a little more. Fingers crossed it continues.

MrsMwa said:

e.g maybe if I spoke clearer then my non verbal child would learn to talk or if we exposed our child to busy family gatherings (we have big families) then they would stop being sensitive to loud sounds or not become over stimulated by busy environments. Or if i took my pre-natals my child would not be disabled

We've faced very similar comments and not just through family or friends, but also from schools and even some medical professionals. It's difficult. The comments hurt and sometimes you do end up questioning yourself, too. But it sounds like you are doing an amazing job with your children and not only recognising their needs but actively supporting them. Don't lose sight of that. 
Wishing you and your family a very Merry Christmas and fantastic start to 2022.