In my rookie semester teaching classes in both Old and New Testament I chose to avoid using a single textbook. First of all, the textbooks used at the college-level as exactly that: college-level. I am unaware of an academically inclined textbook designed for high school classes in biblical literature. Second, even if I did find a suitable textbook, I would have to avoid assigning too much secondary reading. I want my students to become familiar with samples of the primary sources, so 150 pages is about the maximum I would be able to assign of secondary reading.
I have derived an alternative. I will be using articles from Bible Odyssey instead. Most articles are 500-750 words, so that is about 1-1.5 pages each. Over the course of a semester I can introduce about 110-120 topics while having them read no more than 125-130 pages of secondary literature.
Of course, this is an experiment. We shall see how it goes.