The Lesson / La Sylphide, Royal Opera House, London

Great Danes with new tricks

The violence comes with The Lesson, but La Sylphide provides the evening's substance. The Lesson has been gleefully reported as a shattering serial-killer gore-fest, not suitable for children, and not to be performed at matinees (it has been replaced by Ashton's Les Rendezvous). Flemming Flindt's 1963 ballet, based on the play by Eugène Ionesco, is, in fact, a ghoulish cartoon. Kobborg first staged it two years ago, in Out of Denmark.

Confronted by a sugar-sweet dance student, an unhinged teacher bullies, manipulates and finally murders her. But these aren't real people, and you can't care much about them.

The tone is set by the rehearsal pianist, buttoned-up and frumpish, who stalks about the stage in something like a Groucho Marx walk. Zenaida Yanowsky, who danced the role in Out of Denmark, is a fabulous mixture of gawkiness and control. As the teacher, Kobborg is creepily awkward, all lank hair and slack mouth. Roberta Marquez makes an irrepressible pupil, bouncing back like a ball when pushed. By the end, she's limp and terrified, out cold almost before he strangles her. It's a slick, nastily effective ballet.

La Sylphide, revived to celebrate the bicentenary of the choreographer August Bournonville, is the oldest ballet to survive in international repertory. The first version, made in 1832, changed balletic fashion overnight, bringing in a host of ethereal heroines, forest glades and anguished heroes. Bournonville was so impressed that he went home to Denmark to make his own version, with an appealing new score by Lovenskjold. Kobborg grew up with Bournonville's ballet. It is a major acquisition for the Royal Ballet, who dance it with care and confidence.

On his wedding day, the Highlander James is lured away by a sylph. When he tries to pin this intangible creature down, using a magic scarf, she dies. The scarf, we know, has been poisoned by the witch Madge, but that has less impact than the sight of James binding his beloved. Torn between the real and the unattainable, James loses both.

The world of La Sylphide is very real. A group of Highlanders walk on, and they are immediately believable. The men look at ease in their kilts, relaxed and natural: a community on stage. But Soren Frandsen's set designs, made for the Royal Danish Ballet, are unevenly realised, with clumsy scene-painting in the first act. The second-act forest, though too strong on turquoise shades, is fine. The ballet's 19th-century special effects - including the Sylphide's exit up the chimney - work well.

Bournonville's choreography is irresistibly buoyant. Dancers skim across the stage in fast, beaten steps. Preparing to celebrate the wedding, everyone breaks into a reel, all neat footwork and springy jumps. Kobborg and Sorella Englund, once a celebrated sylph, have taught the ballet well. The corps of sylphides have beautifully soft, romantic arms. In the reel, steps are as bright as the silver buckles on the dancers' shoes. (I wish Alan Barker's conducting was as fluent. On opening night, several climaxes were muted by stodgy pacing.)

Alina Cojocaru, tiny and light, is an enchanting Sylphide. She hangs in the air in floating jumps, and flutters from mischief to wistful sorrow in an instant. Cojocaru has troublesome feet, but she uses them gorgeously, every step burnished. Ivan Putrov is still adjusting to Bournonville's style; the dancing is already smooth and clear. Englund is bleak, bitter and dryly funny as Madge. Gurn, James's rival, is sharply characterised by the lively José Martin, with dancing to match: as he jumps, Martin has time to unfold his legs slowly before landing.

In repertory to 9 November (020-7304 4000)