What exactly is it? I teach in Texas and have never heard of it. Here (and this may vary by district even within the state) you get a one year contract your first few years. After that, if you have proven yourself your principal can offer you longer term contracts (3 or 5 years, I think). If you leave your district and go to another, the process starts over. Once you are at the end of a contract, be it a 1, 3 or 5 year, your contract can be non-renewed at the district's discretion. Is tenure different than this?