As a classroom teacher, I am a firm believer in daily journal writing in the classroom. I have seen many benefits come from this practice, and do highly recommend writing in a journal on a daily basis.
Here is a list of benefits that can be gained from including daily journal writing in your regular routine, especially if you are at the elementary or middle school level, while you are still building the basic skills.
Normalization. Writing is no longer something that is "special," done only for assignnments or reports. It is something they do every day, so that they are becoming better writers without even knowing it! For students with any fear of writing, the daily practice quells those fears, pulling them over into authorhood, and lulling them into making writing a safe activity, instead of something to be feared.
Writing in journals on a daily basis normalizes the writing process for students, especially important for those who say they don't enjoy writing. The comfort they gain in writing in their journals can then be transferred to more formal types of writing.
Connection. Students can write about their feelings, ideas and thoughts, and you can provide a listening ear by brief comments on a regular basis. This quiet practice of give and take happening on a weekly can help to calm the atmosphere of your class and prevent blowouts.
Getting to know your students allows you to relate to them more as individuals, during any small group or one-on-one time you have with them. It may also give you ideas for lesson planning with student interests in mind.
Routine. Building routines into your day is the way students know what to expect when they come to school, and therefore will respond themselves in more cooperative manner. Routines keep your students organized and help them to become independent learners.
Routines also help you as a teacher stay organized and able to cope with all the myriad of events that can happen in the day of a teacher. Journal writing done at a regular time every day can be something that the kids look forward to, wondering what the question will be for the day.
Personalization. As teachers, we try to teach to individual students but it's difficult and usually impossible, to do so. Daily journal writing personalizes the lesson by allowing students to write freely on a given topics or a topic of their own choice. Your expectations and feedback can vary by student, allowing you to have a perfectly personalized lesson.
History. A journal allows the students to have a record of their life. Just as we sometimes enjoy going back to see how much our lives have changed, so do students enjoy taking a look back at previous entries, remembering their past and at the same time, subtly seeing how much they have grown.