This summer I got to meet Lyon Terry, my state’s teacher of the year for 2015. Lyon told me about something clever he does in his classroom at the beginning of each school year: He takes a big piece of paper and draws an arrow on it, pointing up and to the right, and labels it the Learning Line. He puts a dot at the bottom of the arrow and labels it “Birth.” He puts another dot a little farther up, for 4th graders. Then another one for high school graduates, and one farther up—but not at the top—for himself.

I love Lyon’s idea of a learning line for lots of reasons, most of all because he doesn’t put himself at the top. He leaves himself room to keep growing.

I started thinking about the learning line when I sat down to work on the speech I gave last week to our foundation’s partners in education. I realized that the learning line is a great metaphor for the work we’re doing with teachers.

Just about every teacher I have ever met is dying to get useful feedback and tools that help them improve their work in the classroom. Unfortunately, they rarely get either one. In a survey (pdf) of more than 1,300 educators, large majorities said the professional development they do isn’t related to their work in the classroom and doesn’t help them become better teachers. In some places, the teacher-evaluation system isn’t even tied to helping teachers improve their skills—it’s mainly used to decide who gets hired and who gets fired.

In other words, most teachers have to move up the learning line on their own. So they proceed slowly. That’s frustrating for the teachers. And it’s a big loss for their students, because the evidence shows that having an effective teacher is the single most important in-school factor in student achievement.

This is an urgent problem. Right now, only 25 percent of Hispanic students and 10 percent of African-American students graduate from high school ready for college. We need to be at 80 percent for all minority and low-income students.

If we’re going to solve this problem, we have to create outstanding feedback and improvement systems for teachers. We need to help all teachers move up the learning line faster, and together with their colleagues, so they can help far more students graduate ready for college.

The good news is that we have learned a lot in the past seven years about what great teaching looks like and how to spread it. At a time when nationwide scores on the ACT and other tests are flat or going down, students in several school districts (such as Denver and Memphis) and states (such as Kentucky) are making impressive gains in learning. So are students in some charter schools.

What all these places have in common is that they excel at supporting teachers. For example, they train and certify classroom observers. They combine various ways to measure a teacher’s effectiveness, including classroom observations, feedback from their classes, and students’ improvement on test scores. They provide teachers with classroom tools aligned to the Common Core standards. And—this is crucial—they focus the teachers’ job evaluations on activities that help them improve their skills.

Now we need these best practices to be adopted in lots more districts and states. I just wish I could be more confident that will happen.

The progress so far is fragile. In places where feedback and improvement systems are well designed, they’re generating excitement, and teachers are embracing them. But in places where the system holds teachers accountable without giving them the support they need to improve, teachers are pushing back, and students are losing out on the opportunity to make big gains in achievement.

So we have to find ways to take what’s working in a few places and spread it much more widely. In my speech last week I encouraged teachers to demand excellent feedback and improvement systems, and I urged state and local leaders to deliver them.

I believe we can do this, if we stay focused on the goal of promoting effective teaching everywhere. You can read my full speech here.