That William Shakespeare, he sure can write a groin injury joke, can’t he? Anyway, that’s the impression you get from “She’s the Man,” a modern take on the Bard’s cross-dressing comedy, “Twelfth Night.”

All that survives the transition from the Elizabethan era to the Britneyan era are a few character names and the gender-bending plot: Amanda Bynes plays Viola, a high school soccer player who pretends to be her own brother so she can play on the boys’ soccer team. Mistaken identities, romance and that groin joke ensue.

This sort of thing has been done much better — “10 Things I Hate About You” and “Get Over It” are wittier, smarter high school comedies that are based on Shakespeare’s “The Taming of the Shrew” and “A Midsummer Night’s Dream,” respectively. “She’s the Man” loses the most important part of Shakespeare: his insight into human behavior. So we can’t tell, for instance, if Viola is a good soccer player, which is crucial to understanding her, and the movie can’t decide if she’s a confident trailblazer or a boy-crazy dip.

The problem may be Bynes, who is the movie’s biggest name but who is also miscast. Her self-deprecating wit isn’t a good fit for Viola, because it makes her seem surer than she is supposed to, and the movie wants to use Bynes’ trademark pratfalls, even though they don’t make much sense for someone who’s supposed to be so physically assured.

There are hints in “She’s the Man” of an interesting theme — that, in 2006, there are lots of different paths for high school girls to take — but the movie shifts away from that and heads toward a generic stew of Abercrombie & Fitch shirtless boys, Nickelback knockoffs on the soundtrack and stodgy scenes that made me think the director showed up on the first day, said, “Point the camera at whoever is talking” and then took off for Fiji for the duration of the shoot.

Bynes is always interesting to watch, but the script makes her work too hard. The result is like a basketball team with one superstar and a bunch of semi-adequate role players who can’t keep up. To paraphrase the real “Twelfth Night”: “Some movies are born great, some achieve greatness and some wouldn’t know greatness if they tripped over it.”