Is it illegal for one parent to enroll a child in preschool without notifying the other parent?

I just found out last night that my ex has had our 2 and 1/2 year old son in preschool since June 1st and neglected to inform me. We have split legal and physical custody, I have 60% and he has 40%, so our son is only in school 3 days a week, every other week. I recently started working full time, I only worked part time at night and I did not need childcare. I started a full time job in the middle of May, and put him in daycare, while still looking for a preschool I liked. My ex is required to pay 1?2 of my childcare, and I am required to pay 1/2 of his. He has never needed childcare for our son because his mother watches him. 2 weeks after I put our son in daycare, he enrolled him in preschool to avoid having to give me additional money for daycare, and did not inform me. Is this legal? I am planning on enrolling our son in preschool in the next month, is it ok for a child son young to be going to 2 different schools? (we live an hour apart) I am considering going back to court to get full custody.