Yes, school fees are considered direct expenses and are included in the basic child support amount. If you need a reference, look at section II.B.7.a.(1)(b) under shared expense plans. The guidelines clearly state that direct expenses include education expenses. Of course you are also paying for indirect expenses (housing and utilities) for your children and your ex, which is in addition to the direct expenses. It's all rolled into the single child support number.
Where you get into more litigation is when the children attend a high-cost private school or require special education. In those cases, a court can determine whether or not the expenses will be shared and how they will be shared.
It sounds as if you are not bound by any expense sharing plan because the judge ruled it was not filed and would not be enforced. In that case you would usually just be responsible for your income proportionate share of any uncovered medical expenses or things like that.
