If I'm understanding it correctly, there was an incident with one of your children. Both parents were informed. One replied asking for more details, the other said the child had been spoken to. The school felt it had been dealt with and moved on.
You feel the school has taken your ex's side so is now ignoring you. You want to escalate this and complain to Ofsted. Even though, by your own admission, the school is in contact with you when your child is unwell, or a report is sent out.
I think the main issue is that you are aligning the school not responding to your reply with the difficult relationship you have with your ex.
In most cases, the school assumes that parents are able to discuss and resolve matters pertaining to their children between themselves. They don't need both parent's opinions about a small incident if one has said it was dealt with. They don't need to tell you about things which happened on a day your ex is in charge of the children, and vice versa. They don't need to acknowledge you at a school event. It doesn't mean they are ignoring you, it means they have other things on their mind.
You come across as argumentative and aggressive.
If you want more communication you need to speak calmly and explain that you and the ex do not share information, that the situation is very difficult and although you recognise it may be a pain for them, you would appreciate all information being sent to both of you.
To be honest, for most parents, the only communication they receive regularly is PTA requests, school trip money requests and reminders about non-school uniform days. They don't send out regular updates about a child's day etc as it would be completely unmanageable.
If a parent is in regular contact with the school it is because the child has SEN, behaviour problems, other safe-guarding concerns or the parent is very needy and is constantly asking about things.