This is one of my favorite episdoes of the entire series. What's not to love?
First off, we have Walker going undercover as a substitute teacher in order to uncover why high school students have been turning up dead and full of steroids. Hilarity ensues as Walker actually takes his new job seriously, much to the chagrin of the students. His pupils perceive Walker as weak, but he quickly lets them know that he has a few tricks up his sleeve. What's also funny about Walker being a teacher are the looks he gets from the principal, who doesn't seem to care for the Ranger's teaching techniques.
Secondly, we have the comically roided up goons who serve as the antagonists for the episode. They are so inept that they give the kids the steroids BEFORE they get any payment from them. Seeing as how these are high school kids and the drugs cost thousands of dollars (which we learn later), no one pays. What's the best way to get money from someone who is indebted to you? Why, kill them of course! The muscle heads even show up at the school to exact their revenge; walking the halls to the objection of no one. One of the goons drives a car with the personalized license plate "BIGGER," which I also find hilarious.
The episode shines largely because of the two factors I have outlined above. The people that play the steroid pushers are perfectly cast for the usual campy Walker villains. My only gripe with the episode is that Walker somehow gets all of the "dumb" students to take school seriously and sign up for the Advanced Placement test all within a matter of days. I can overlook this, as Walker does offer free self-defense classes after school as a reward! All in all a great episode with an aura that is uniquely Walker, Texas Ranger.