Typically you do need to raise your own support. While there are a few exceptions, Teachers In Service works with donation, faith based MK teachers and schools.
• You need to raise your own support because paying teachers a salary means the school has to raise tuition to pay your salary. That means the parents of the children you teach have to raise more support from their own supporters. Since teachers are just as much missionaries as the parents of the children they teach, they should not have rely on parents to pay their expenses.
• Raising your own support solidifies your call* to be a missionary. MK schools and parents want teachers who have been called by God to serve as teachers. Raising support is one way that God can communicate whether or not he truly wants you to teach children of missionaries.
• Raising your own support is a faith-strengthening process. While support-raising can be difficult, God can use it to build your trust in him. Further, it strengthens your own sense of dependence on him as you see him provide what you need.
• Raising your own support provides you with prayer support. When raising support, raising money is only part of the picture, and not even the most important part. You will also be asking people to pray for you and for God's provision and grace in your life. You will find that prayer support crucial during your time living overseas teaching MKs. You need people who are presenting the challenges you will face before the throne of God.
When a teacher stays in mission school teaching for a few years, he/she will return to his/her home country for furlough to renew financial and prayer support. This is a healthy situation for the teacher, supporters, and the home church in general.
Please contact TIS if this answer did not completely answer your question.
* In him we were also chosen, having been predestined according to the plan of him who works out everything in conformity with the purpose of his will. (Ephesians 1:11)