In the real, rough-and-tumble world, those who don’t perform don’t succeed.

It’s a fact of life that good business plans fail every day. Good people fail too, but they learn from their mistakes, redouble their efforts and try harder next time. And invariably, when success comes they give testimony to the fact that failure was their greatest teacher.

But it’s one of life’s great ironies that the rules of success and failure do not apply to the teaching profession itself. Not in Pennsylvania, anyway.

For public school teachers, seniority is the trump card. The longest employed teachers, rather than the best, are most secure in their employment. Under current state law, when a school district faces severe financial difficulty and the prospect of staff reductions, faculty layoffs are based strictly on seniority — the last hired are the first to go.

There’s a move pending that would change that.

The state Senate on Monday voted 28 to 22 in favor of a bill that would require school districts making layoffs to first eliminate teachers deemed to be failing or in need of improvement, rather than those most recently hired.

Four years ago, the state introduced a teacher performance rating system. Under the pending bill, the teacher ratings would guide decisions about layoffs and reinstatements.

Gov. Tom Wolf opposes the change and he’s prepared to veto a bill that would remove seniority as the sole deciding factor when districts face layoffs.

Grading performance is not a foreign concept in academia — students and teachers alike understand what it takes to earn A-level grades and a 4.0 transcript. From the earliest age, students are taught to associate reward with competitive, top-of-the-class performance.

A great lesson, right? Except teachers don’t want to apply the concept of competition — or even of competency — to themselves. They expect their unions to protect members who might be incompetent, not suited to the classroom or even lazy, at the expense of teachers who might be younger and have fewer years of dues-paying membership.

And the Democratic governor, who enjoys support from the teachers unions, doesn’t want to upset that equilibrium. Officially, his office says the issue should be settled by districts during negotiations with labor unions. Not that existing law allows any negotiation on this issue, since seniority is the only factor allowed to be considered.

Maybe students should form unions and negotiate a C-plus grade across the board, too. It would make about as much sense to average out the students’ performance as it does to average their teachers’ performance the way we currently do.