Together Everyone Achieves More

When teachers work together, their objective is for all students to learn. In collaboration, everyone must benefit. When teachers compete against each other, one may think that students' learning outcomes can likewise improve. Unfortunately, in every contest, there is a winner and there is a loser. And winning can be simply based on having one's students outperform pupils of some other teachers. In basketball, soccer, or football, the fumbles of one team turn into trophies for the other team. For this reason, competition-based policies such as performance based bonuses can poison public basic education.

These are not just mere conjectures for there is evidence from research that when teachers collaborate, when teachers work as a team, students gain. A paper published in the American Educational Research Journal, "Teacher Collaboration in Instructional Teams and Student Achievement" looks at data obtained from over 9000 teachers in 300 Miami-Dade County public schools, and arrives at the conclusion that in schools where collaboration is of high quality and is helpful to teachers, students' performances in math and reading are enhanced.

Above copied from AER
The answer to why there is a correlation between quality collaboration among teachers and students' learning outcomes is perhaps captured by the following slogan from Literacy in Learning Exchange: