For practice on the writing and essay portions of the SAT/ACT, do the work in the packet “Grammar For High School: A Sentence -composing Approach” (by Heinemann of Houghton Mifflin Harcourt). Then practice, practice, practice on your own! In essays at school. In free-response at school. In sentences written here and there. In emails. In text messages. Do it!
An explanation of how to teach that way and of the rationale for it is in The Teacher’s Workbook.