How do I ensure reading comprehension?

This is my 2nd year homeschooling and using your history program with my middle schoolers. One question I still have is after the students have done their reading assignments, what do you suggest parents do to make sure the children have understood and grasped each reading? So far, I do the readings first and then we discuss as a family. I am not sure this is enough.

I understand your concerns about the reading. Discussion is extremely valuable and if you have the time, using the open-ended or Socratic method, as illustrated in our Teacher's Guide, is very useful.

When I was homeschooling I also used simple book report forms to lead my children through examining the books they read. We didn't do it with every book, because I wanted plenty of their reading to be for pleasure rather than "school." However, analyzing books is also an important skill for teaching critical and creative thinking skills.

Below are some resources for your consideration (don't panic and try to do them all!). Sprinkle some in here and there as you have time and the kids have an interest.

Here are some simple templates for middle school reports that are helpful for this kind of work. You can download and use them for free:
https://www.template.net/business/report-templates/middle-school-book-report-template/ 

We carry literature analysis guides for selected books from Connecting with History here:
https://www.rchistory.com/Connecting-with-History-Literature-Guides-s/383.htm 

There's another skill called Character Mapping which can be helpful. Here's a simple explanation:
http://www.readingrockets.org/strategies/story_maps 

Here are a set of templates you could use for character mapping
https://www.literacyleader.com/sites/default/files/Character%20Graphic%20Organizers.pdf

Here are lists of open-ended questions that can be used (no need to use all of them - just a few to get the ball rolling!)
https://minds-in-bloom.com/20-literature-response-questions-for/ 
http://cmepta.org/wp-content/uploads/2016/07/CNC_Open-ended-questions.pdf 
https://mseffie.com/iOpeners/Open_Questions.pdf 
http://decal.ga.gov/documents/attachments/Questions_Children_Think.pdf