The main part of the Shakespeare in Three Steps books is divided into lessons, with each one requiring 20 minutes or fewer (Step 2). If you download a sample and look at the Contents page, you’ll see how the Acts and Scenes are divided into lessons. Then if you add one lesson at the beginning for Step 1 (to read the story version) and one lesson at the end for Step 3 (to watch the play performance), you would have your planning done. Most of the plays we have available so far can be done in a term (12 weeks).
Studying a Shakespeare play would certainly count toward a high school literature credit, but I don’t think it would amount to a half credit by itself. If you’re going by time involved, a half credit would require about 60–75 hours of work. Working through Macbeth, for example, would take only about 7 hours all together: 20 minutes each for 11 sessions, then 3 or so hours to watch a full performance.
I hope this helps!