This is a matter to be handled by your attorney. If you do not have one right now, you should consult with one ASAP. The answer lies partly i your parenting agreement but you really need to return to court for clarification and possible enforcement. Generally, child care is a separate financial burden from child support. You are fortunate that there are many excellent family law practitioners i your county.
if you have sole custody you may make decisions on education health care and religion by yourself.
if you have joint custody, the other parent is involved in the decisions and you must agree before implementing a decisionl.
if you have correctly quoted the language in the court papers, you make the decision, she pays. but if the additional school time is on her parenting time, then you cannot do this without her agreement.
or, if there is some language that requires agreement before she is obligated to pay, you cannot do this without her agreement.
take your papers to a lawyer for a review and asks the lawyer to read in re the marriage of charous and then advise you. do this before you increase the daycare time and expense.
If you have sole custody, the decision as to the daycare provider is within your power. If there is no requirement to obtain her consent or agreement before she is obligated to contribute, then she may be in violation of the order if she does not pay.
Even if there is joint custody and she simply refuses to pay for child care when the child is going to the same place he has always been going you likely have a strong case for enforcing her obligation to pay. I have seen numerous cases where the parties had joint custody, disagreed on an issue that involved cost and neither party sought court intervention. Later the party paying the cost would seek reimbursement under the terms of an order requiring reimbursement and the other party would object because they didn't agree (arguing the act of moving forward with implementing the decision was a violation of the JPA and therefore should not justify reimbursement). Unless the order specifically required agreement before the right to reimbursement, the other party was usually ordered to pay.
if you judgment states that your ex is responsible for 50% of daycare that is not to come out of support. She is responsible for day care independent of support. She is responsible for child support as well until the court says otherwise. Good luck.