They haven't been charged with animal cruelty; they've been charged with misdemeanor grand theft for stealing the koi, and vandalism for the injury to the other fish in the pond they caused in the process. (see this LA Times article)

As always, I've got a full list of links to news stories here.

And the estimated value of this particular fish I've seen in every news article is $750, not $300. Supposedly, the boys reimbursed the school $650 for it already, although I don't think I could place a value on the life of a pet. ALSO: I think it's funny that brother Casey was interviewed by the press, when HE WAS THE ONE who committed the theft. So I'd have to say that any statements he makes are not the most reliable source of information, and may be partially (if not wholly) self-serving.

I think if you'll check legal decisions that judge the value of a pet, you'll find that the value of a pet is not measured in emotional attachment. Therefore, the figure of $750, if that's what it was worth should be sufficient.

I have a feeling that their peers will exact a much greater punishment upon these fellas.

I think if you'll check my post, I made no representations about what the state of the law regarding the value of a pet is. I said, "I don't think I could place a value on the life of a pet." (emphasis mine) However, I would be glad to bring legal precedent into the discussion.

Basically, your theory about the state of the law is not universally correct, especially depending upon the particular jurisdiction and type of action.

There are two separate potential civil causes of action when a pet is intentionally killed: (1) financial recovery for the value of the pet, and (2) equitable relief. In the case of #1, your supposition is correct: the value is almost always the market value of the animal (plus any expenses or medical bills). However, in #2, your supposition is dead wrong: the emotional value of the pet, and the emotional damage to the owner, is not only often taken into account, but will likely be the main determinant of damages in many instances. Owners have successfully sued under a variety of theories in case #2 -- conversion, infliction of emotional distress, loss of companionship and trespass to chattels.

I'm not arguing that a lawsuit in this instance would be successful (or even meritorious), but the notion that the legal value of a pet is ONLY its replacement value is false.