It's midseason for that entertaining harbinger of Western Pennsylvania spring, the high school musical. It's midseason for me, too -- Avonworth High School's "Into the Woods" is the third musical of the six I will write about this spring, and it's the best so far.

This is of interest because Avonworth is one of the relatively few high schools -- about one out of seven -- that run their musicals for two weekends: You can still see "Into the Woods," tomorrow or Saturday.

It's the best I've seen this year in several ways. To start, Stephen Sondheim's lush score and his and James Lapine's clever, poignant adaptation of famous fairy tales make it one of the great musicals of the past quarter-century. Although its musical and story-telling complexity are difficult, Avonworth handles it with great success and better acting than the high school average. So "Into the Woods" also provides the richest audience experience.

But perhaps not for all audiences. I went to Friday's opening, which isn't usually the best time to see a high school show. Given my affection for "Into the Woods," I tried to keep my expectations low.

I needn't have -- this show is in good hands. Only the audience didn't seem up to its demands. My guess is that people expected a fairy tale revue, so the twists with which Mr. Sondheim and Mr. Lapine adapt and interweave the tales, including one they make up completely, along with the clever dialogue and lyrics, caught them by surprise.

But about halfway through Act 1, with "Agony," the comic duet between Cinderella's and Rapunzel's princes, the audience seemed finally to catch on, laughing and applauding at the level it deserved.

From then on, it was pretty clear sailing, allowing me to relax and share in the fun. That means marveling at the wisdom of these familiar fairy tales. You recall that they were never meant just for children, being full of family dysfunction, revenge, passion, perversion and murder, in addition to triumph and happily-ever-after. As plumbed by the Brothers Grimm, they are full of Freudian insight, and Mr. Sondheim and Mr. Lapine embrace that, adding good humor.

So these woods are full of imagination, fantasy and libido. It's a show you can take children to, but you'll be glad that the more suggestive lyrics and double-entendres will go right over their heads, like those of Little Red Riding Hood and her Wolf.

In Act 1, a Narrator (the mature and unctuous R.J. White) introduces us to the full tales of Jack (Isaac Miller), Cinderella (Chelsea Stewart), Red (Rachel Pool) and the Baker and his Wife (Nico Alfonso and Lauren Harpst). This last is the invented story: The couple has been rendered barren by a Witch (Andrea Weinzierl), who says she'll lift the curse if they come up with three objects.

Everyone leaves home for different reasons and heads into the woods, i.e. unpredictable, scary life, where the quest of the Baker and his Wife entangles them with all the others, not to mention princes, stepsisters, a wolf, Rapunzel, Jack's mother and a mysterious man. With wit and cleverness, the stories all end happily: by itself, Act 1 is a perfect one-act musical.

But there are repercussions. In Act 2, the mother of the giant Jack killed shows up for revenge. The accepted stories break down. Characters are exiled, blinded or die. They even turn on their Narrator. In this post-apocalyptic world, the survivors have to form a new kind of family (think of "South Pacific").

Act 2 isn't as much fun as Act 1, but it's the necessary corrective, rich in wisdom and moral complexity. "Sometimes people leave you, halfway through the wood," goes a lyric; but "you are not alone, no one is alone."

Producer/director Deborah Frauenholz, who also designed the set and co-choreographed with Ashley Wickert, leads a capable creative team. All the movable platforms seem unnecessary, but the woodland backdrop is pretty and the many lavish costumes look great under Bob Steineck's lights.

Jennifer Rapach's orchestra of 12 students and seven adults gives a good account of Sondheim's lovely music. But as is often the case with high school musicals, the mics were sometimes balky. That and the intricacy and speed of some of the lyrics probably damped that opening night audience response.

Ms. Weinzierl is a self-composed and commanding Witch, not to mention as beautiful, when she sheds her years in Act 2, as a pre-Raphaelite painting. Her singing is fine, but her acting is even better. Mr. Alfonso's Baker is sweet and concerned, while Ms. Stewart's Cinderella has a lovely voice. Among the audience favorites were those Princes (Houston Hunt and Casey Cunningham), but most of the actors merit praise.

For some schools, it would be a drawback that "Into the Woods" has no large chorus numbers, but Avonworth is small, and Ms. Frauenholz has added some high-stepping horses, woodland sprites and fugitives from other tales to inflate the cast.

As deep as it is wise, funny as it is sad and smart as it is earnest, "Into the Woods" easily justifies its three-hour length. There's a lot there to love.

For more pictures of "Into the Woods" and further coverage of high school musicals, including Kelly Critics reviews and a master schedule, visit post-gazette.com/theater.