:iagree:
HOP K level covers CVC words and a few sight words. That's OPG up to lesson 40 (sections 1-3.)
HOP Levels 2 & 3 (orange and red) are suppose to be 1st grade. Both deal mostly with consonant blends, OPG lesson 41-63 (sections 4 & 5.)
HOP Levels 4 & 5 (green and blue) are suppose to be 2nd grade. They cover R-changed vowels, which is started in lesson 154 of OPG (section 16), but they don't cover most of OPG's section 15 (Silent letters.) HOP also introduces compound words in level 4, when OPG doesn't until Section 17 (out of 25 sections total in OPG.) HOP 4 mostly cover silent-E words, vowel pairs, plus R-controlled words, and introduces smaller compound words at the end (plus more sight words than OPG.) HOP 5 covers more, less common vowel pairs, plus shr, str, scr, spr, spl, squ, and soft sounds of c and g, which were already covered in sections 6 & 7 of OPG.
I would consider anything in OPG Lesson 134 (section 15) and up to be 3rd and 4th grade.
I hope that helps!
Added 12/6: this inspired me to make a blog post about how OPGTR and HOP compare. It contains more in-depth information than this post, for those interested.