District Trendline, previously known as Teacher Trendline, provides actionable research to improve district personnel policies that will strengthen the teacher workforce. Want evidence-based guidance on policies and practices that will enhance your ability to recruit, develop, and retain great teachers delivered right to your inbox each month? Subscribe here.

From the basics like length of school year and planning time to the big decisions like teacher tenure and layoffs, Teacher Trendline covered many key topics in district policy throughout 2016. This month, we take a look back at some of the highlights.

A day in the life…

Over the course of the year, Trendline took a look at those policies that have the greatest impact on teachers' daily lives in the classroom such as how long the school year is, what restrictions districts place on class size, and how much planning time teachers receive.

On average, teachers who work at the districts in our database work 187 days per year, with the vast majority going back to school in August.

Teachers are scheduled to work for seven and a half hours each day, on average, with at least 45 minutes of planning time per day.

Roughly two-thirds of the districts in the Teacher Contract Database set some type of class size restriction, dictating how many students a teacher will have in her classroom. Among districts that set specific class limits, average class size caps range from 20 students in pre-kindergarten to 31 students in grades nine through twelve.

The importance of tenure

Tenure is an important decision point for districts that impacts more than just whether or not a teacher continues to teach. In 54 percent of the districts in the database, teachers are awarded tenure after teaching for three years.

Almost one third of districts vary the number of observations required per evaluation cycle by a teacher's tenure status.

Roughly 45 percent of districts in the database use tenure status as the starting point for making layoff decisions. While the majority of districts offer teachers recall rights that give laid-off teachers a preference when the district begins to hire again, there are 17 districts where only tenured teachers have these rights.

Want to read more? Use the links below to access the full version of all of 2016's Teacher Trendlines. If you see a topic we missed in 2016, make sure we don't miss it in 2017! Send your ideas for future editions to teachertrendline@nctq.org.

January: Layoffs

February: Chicago contract negotiations

March: Observations

April: Teacher transfers and mutual consent

May: Teacher tenure

June: Substitute teachers

July: Planning time

August: Student and teacher school year

September: Teacher leave

October: Class size

The Teacher Contract Database includes information on over 145 school districts in the United States: the 60 largest districts in the country, the largest district in each state, the member districts of the Council of Great City Schools, and districts that won the Broad Prize for Urban Education. The database features answers to over 100 policy questions and provides access to teacher contracts, salary schedules, and board policies in addition to relevant state laws governing teachers.