Cancel of visa and transfer to school visa

Hi
My children are under m y visa . I want to transfer them to the school visa .
Please let me know how I can cancel the previous visa as soon as possible

Thank you

Under your visa, meaning dependent visa under you, is it?
If you are under EP, you can actually refer to your company HR who deals with visa application. They shall be able to proceed to shorten/ cancel the dependent visa.

Meanwhile, please explain the current situation to the school. Usually, immigration will not simply cancel the visa, they need supporting documents from the school as proof.