Subject of "lead" ?

Hi~ figuring out subjects of "that clauses" is sometimes confusing. Here what can be the subject of the word "lead" in this writing? Any idea will be welcomed. Thank you~!

Teachers can promote higher-level thinking by utilizing activities that force the brain to make desired connections
without spoon-feeding students solutions. Think of instruction in terms of a jigsaw puzzle. The core information is the border pieces that provide a frame to help better solve the puzzle. The very distinct objects in the puzzle
are the principles and applications taught through embodied cognition. These are often easier to see and assemble. Higher-level thinking is the remaining pieces that are more nebulous. These puzzle pieces would be
impossible to put in place unless all the prior work had transpired. This is why teachers should create activities after automating core information and promoting concepts through embodied cognition that lead students to
assemble the essential components learned and arrive at higher-ordered conclusions on their own. Higher-ordered thinking is, in fact, the evidence that the instruction has taken hold.