Are board initiatives the same in High School and Elementary School?

Why is high school so different than elementary school from a teaching ideology perspective?  Today I had pleasure of working along side high school math teachers for a ministry grant focused on the transition from grade eight to nine.  They were so impressive and we had such rich discussion about our   teaching styles and philosophies. The more layers we unpeeled, the greater differences we saw. 

For instance, many boards (elementary) really push critical literacy and inquiry as the best model for student growth.  The focus is on reducing the amount of teacher driven instruction and increasing the amount of student driven instruction and collaboration.  The high school model seems to have different initiatives and it makes me question that if what elementary does is based on research, why are high school not doing the same?  I am not saying that what they are doing is not based on research or not effective, but it must be different research. 

It is strange to me that entire school boards would not support the exact same initiatives throughout if they are what is best for students.  It almost feels like it is two different companies, at times, under the same name.  I applaud my board for looking deeper into this, but I still question how the two systems are where they are regarding this, and who is really doing what is best for our learners?  Do you guys have any insights or opinions on this?