Consider asking parents to write you a letter about their child. A personal letter from the people who know your student best can inform your teaching for the entire school year.
Many letters will be straightforward: basic info about likes and dislikes, favorite subjects, etc. However, some parents will be glad of the opportunity to share special concerns. You might learn about family circumstances, health issues, or previous experiences with school that affect how the student learns and behaves.
Be judicious about whether you request a letter from families. At some schools, parents would welcome the chance to communicate in writing. At others, parents may feel like you are giving them a writing assessment. Another possible issue is a language barrier–but you never know. You might find that some parents are happy to write you a letter in their native language. Chances are that someone in the district can translate for you–or you can get a rough idea with a Google translation.
Back to school night is a good time to request the letter, but it’s not the only opportunity. Your school might have an Open House a few weeks into the school year. By that time, the rush is past and everyone, including you, has more time to devote to the assignment.
A clear complement to the letter-from-a-parent is the letter-from-a-student. An open-ended letter about the student makes a good writing assessment and informative piece for your files.