Decisions for children with special needs

I have been divorced for 7 years, and have primary physical custody of my two daughters (now ages 12 and 13). My youngest was diagnosed with autism at age 3.
She has been struggling with school since going to middle school this year. I would like to send her to a private school specifically for autistic children.
Her father has stated that he does not agree with this decision. He says that he is unwilling to help pay tutition for private school. I have applied for a grant which will cover the tuition. He still does not agree with pulling her out of public school, and enrolling her in private school.
Can I legally enroll her in the private school when he states that he does not agree with that decision?

Do you have a court order or agreement on custody? If so, look at the document to see who has decision making authority. If you do, then you certainly can make a unilateral decision about school. The order or agreement should state who has legal custody/decision making authority.

Thanks for your reply. Our agreement states that we will have "joint control over decisions regarding each child’s care and education, and with each parent having an equal voice in decisions relating to their health, religious training, vacations, choice of schools, summer camps, and other living experiences."
Therefore, I am not sure of how to proceed, or how to resolve the situation with my ex.

If your agreement states that you have joint decision making power, then you cannot unilaterally change the child’s school. You can file a complaint for child custody to get a court order on custody and ask the court to include in the order either that you be given sole legal custody (decision making power), or ask the court include in the order that the child is to attend the school you want her to.