Each school will submit a letter of introduction to the project. We would appreciate your limiting the letters to one per school.
Letters can be any length.
Some teachers have their class as a whole write the letter and other teachers assign it to a couple of students. Or you may have everyone take a stab at the letter and then select the best one. Some teachers even write the letter themselves. Do whatever is best for you. Feel free to look at examples from a previous year's project.