My landlord is withholding my security deposit because he says we ruined the carpet. The carpet is a bit dirty and worn in places, but it was not in great shape when we moved in. Does this fall under "ordinary wear and tear"?
Unfortunately, there is no precise definition of the poetic phrase "wear and tear." One commonsense definition would be this: Ordinary wear and tear is what a reasonable person would expect to see after tenants have lived in the unit for that amount of time, assuming that the tenants took reasonable care of the premises. Of course, you will need another dollop of common sense to divine what reasonable means in this situation.
It does not mean that the rental has to be scrubbed with a bleach-dipped toothbrush; nor does it mean that a tenant who has used the unit as an artist's studio employing the Jackson Pollock spatter technique can expect to leave without paying for cleaning and repairs. In the last analysis, when a conflict persists, what is ordinary wear and tear may be what the small claims court judge decides it is.
And in your case, the answer will depend on just how bad the carpet is and whether you can prove what its condition was when you moved in. Did you and the landlord do a walkthrough when you moved in? Did you fill out a move-in checklist to record damage that was pre-existing? If so, these things will help you in court.
Is the landlord charging you for carpet cleaning or replacement of the carpet? Unless you absolutely destroyed the carpet, a small claims court judge would no doubt say the landlord has no right to charge you for its full replacement cost (assuming you can prove its condition was not pristine when you moved in).