Minor rant time. Many times unconvential high school teaching techniques get a frowny face from established teachers because "it doesn't prepare them for college." I would argue maybe 10%, 20% if I'm generous, of the high school experience in any way mirrors the college experience. You go to classes, there are people in them, and someone delivers instruction. As far as how the material is digested, I don't see how they're similar at all. Let's ignore the crazy costs of textbooks you may or may not use, the up and down quality of instruction and faculty who are only dependent on bringing in research dollars. And that failure rates, state test scores, active engagement, and observations play no part in keeping their teaching positions. Often incoming faculty will negotiate the least amount of teaching possible to prevent distractions from research.
Now, I enjoyed college, I had more good teachers than bad, but regardless of who was teaching, a college class assumes absolute mastery of previous material. If you lack mastery, you have a lot of free time to practice. Your performance is incredibly dependent on what effort you put in. If you don't care, your university will happily cash your check and show you the door. It's a tough lesson to learn.
If you really wanted to prepare kids for college, the ones that don't try would be shown the door. Good luck getting a public school board to approve that.
The part I want to get at though, is the assumed mastery. Any high school teacher at any school will tell you that most students do NOT have mastery of the previous material. And yet I can't tell me how many "they don't know anything!" and "how could they forget that!?" rants I've listened to like it's a shock. They're kids. They're 15, 16. They only recently stopped having a bed time. You're telling me someone that age with a Spongebob backpack is supposed to be an abject master of Algebra I and Geometry when they walk into my room?
College has a way of making you forget what it was like to be in high school. You had to step up your game or it was all over. Some back of the envelope math to consider (high school stuff based on the mixed block we use at my school):
College is a frenzy because it has to be. Class time is all lecture because you have half the time to work through much denser material. I considered my time outside of class to be catch up time, it was a chance to get assignments, projects, labs, etc caught up with what was covered in a week. Lecture would arrive and I'd be behind again. Over and over again until the sweet release of December.
If I have 102 more days and an extra 90 minutes a week, why would I force myself into the restrictions faced by professors? Why do I need to lecture 4.5 hours a week? How are my words so important that we don't have class time to pursue mastery? As a high school teacher, why are you wasting your time complaining about mastery instead of putting the effort towards teaching it? Why would I assess their learning so infrequently?
Kids don't know stuff, it happens. Encourage them to learn more, and stop berating them for what they forget.