You really need to speak to a solicitor and seek legal advice
I'm not sure what you're trying to achieve?
I second a hell of a lot of advice you've been given over threads. You can palm the children off on him and then play games like this, along with the fact your ex is playing stupid games with them too
There is no consistency for your children, I can't imagine how confused, scared and upset they are feeling.
You knew there was the biggest chance your ex would be going to pick them up at school today,considering he's having them all week, so why did you go down to the school knowing this?
You're really not doing you or your children ANY favours! You haves means to contact them on their phones,going to the school achieves nothing and it isn't their job to facilitate this.
I guess that now your ex is there this has opened up yet another load of unessessary drama which could have been avoided.
Leave it be and seek advice from your or a solicitor.
You're messing with your children's minds now, they won't know if they are coming or going or who's right and who's wrong.
I'm a single parent to a 16 month old, luckily me and his father get on quite well, if he'd have been acting the way you say your ex has/does, which I don't doubt, even in my time of need, I would not be giving him my son
I really am starting to believe it's not the children's best interest but the drama and shit surrounding it that you want