Back in the 70s and 80s when Star Trek was scoring big ratings in syndication, this episode was a perennial favorite among Trekkers. Each time it was scheduled to air, it gave Trekkers a chance to tell their significant others, "Honey, you're more important to me than Star Trek; let's go out tonight".
This ship-based episode is basically a devil worship story with children, which gives it two elements Star Trek has difficulty handling separately, let alone together. For the part of "the friendly angel", aka, the evil ghost luring children to the dark side, Fred Freiberger uses his friend, super-attorney Melvin Belli, who would seem a wise choice on the surface. Belli, infamous for defending seedy characters such as Jack Ruby, The Rolling Stones, and Jim Bakker and renowned for his oleaginous, hypnotic delivery, comes across on paper as both perfect for the part and a ratings coup all in one. But the stunt backfires, with Belli coming across as more robotic than hypnotic and no ratings boost to show for it. In truth, it wouldn't matter if Freiberger had cast Jack Palance; the part is doomed from the beginning by the weak script. (Indeed, Palance plays a similar role in a 1979 episode of Buck Rodgers in the 25th Century, and even he can't make it watchable).
The heart of the problem is the lack of a central theme or point. The episode itself is sort of like a mashup of "Charlie X" and "Miri", but whereas they each have a focused storyline, this one just meanders along, forcing us to endure a series of scenes of misled children before a climax appears out of nowhere. Meanwhile, the disappointing special effects and wardrobe choices add to the misery, with Belli seemingly wearing a shower curtain taken from a cheap 60s motel... which considering the third season budget might actually be the truth. You can argue that "Spock's Brain" and "The Way to Eden" are hokey, but at least they're fun. "And the Children Shall Lead" lacks any entertainment value and makes a strong case for never having kids... at least in a Star Trek episode. (For all the grief people give Star Trek V, comparing Sybok's takeover of the Enterprise to little Tommy's is like comparing Shakespeare to Captain Kangeroo).
Curiously, TNG does its own version of this story with its seventh season episode, "Imaginary Friend". It's not very good either.
This just gets a vanilla redo with a new Enterprise and new planet (replacing the original's reeuse of the "Operation: Annihilate!" planet). CBS doesn't even replace a viewscreen shot of the Enterprise flying through a tunnel of knives, which you'd think would be about as easy to upgrade as creating a screensaver. (Actually, that's just what the original looks like). But really, why bother? As an internet message board user calling himself "Evil Dr. Puma" writes, "This episode is less in need of remastering than regret, remorse, and