Warriner's English Grammar and Composition, Third Course (for Eng. 2)
This textbook (and this edition) is widely considered the authoritative source, the gold standard, and the last word on all matters relating to words, phrases, clauses, and the structure of the English language.
It has long been out of print, but LOS students will use PDF copies as the basis for the English grammar aspect of this course.
English 1 will use Warriner's Second Course, and English 2 will use Warriner's Third Course.