my kids have to master how to punctuate introductory prepositional phrases

Instead of teaching your kids how to punctuate "introductory prepositional phrases", just tell them to punctuate "introductory phrases".

Problem solved.

You don't have to be a mechanic to drive a vehicle. Learn to drive first, then get your hands greasy under the hood if it suits you. It doesn't suit everyone. Just the suits at the Board of Education.