This math content is crtical to fully understand both conceptually and computationally if students are going to know/understand algebra, geometry, trigonometry, etc., etc. etc. etc. And, it is FREE...but an educator has to read it and think about it.
We taught this methodology successfully to urban, Title 1 kiddos in 5th grade to mastery school year after school year. They got it every single time! These kiddos that are NOT getting this content to proficiency levels - it must be on our end. They must not be able to visualize mentally a postive/negative number line in their minds, and/or the students are conceptually lost in the basics. All can be fixed in short time with proper instruction.
I do a bit of consulting at middle schools from time to time, and I am disappointed I see such ineptitude in our students' understanding negative and positive integers. Upon questioning middle school students, a VAST majority do not understand that subtracting positive/negative integers is EXACTLY the same in physical meaning as they learned in 1st and 2nd grade. I think the mistake is the lack of number line use and sufficient repetition.
This unit helps the teacher with these elements. Folks, the lack of student understanding has to be fixed or America is headed to be a third world country, unfortunately, at some point in the not too distant future. Sorry for the dismal statement, but I am in a lot of schools. It can be really disappointing and disheartening. It does not need to be like that.
Best, Blaine Helwig