This week is Teacher Appreciation Week across the nation, and in Colorado, Vail Valley schools are among those bringing proverbial apples to the teachers. But in Denver, under the Capitol dome, the teachers aren’t feeling as appreciated.

Instead, they’re mired in a fight over Senate Bill 191, which aims to improve their effectiveness on the job by creating an evaluation system that could prevent them from receiving tenure–or they could even lose it–if their students don’t perform well enough.

Now, a rift has emerged between teachers unions over the proposal. The American Federation of Teachers Colorado backs the legislation by Senator Michael Johnston of Denver on the basis that new amendments expected to be introduced today in the House Education Committee send the bill in a “new direction,” according to the Denver Daily News (via State Bill Colorado). The amendments would provide a due process system that allows teachers to appeal evaluations, as well as giving laid-off teachers preferences in rehiring.

But the state’s largest teachers union, the Colorado Education Association, is still ardently against the measure and says AFT mainly represents educators in Douglas County. “They do not represent the teachers of Colorado–the CEA does,” says CEA spokeswoman Deborah Fallin. The bill heads to a House committee this afternoon, according to Westword.