A letter that a teacher writes to parents is very pointed, getting to the main purpose right away. This kind of letter is written with a personal business letter format, in a modified or semi-modified style, and maintains a professional tone throughout. The letter's intent is always to further engage the parents in their child's scholastic development.
Teachers may request a meeting with parents to discuss a child's behavioral issues. Perhaps the child isn't doing well on tests, is talking too much during class, is missing assignments, is being uncommunicative or isn't getting along with the other students. A letter requesting a parent-teacher conference about these matters should state the desire of the teacher to get input from the parents in order to resolve these issues. Teachers can state what's being impacted by the child's behavior, such as the calm of the class or its productivity.
On a more favorable side, teacher might want to inform parents in a letter about an upcoming project the class is participating in. The teachers should provide details: the topic, the start date and end date, for example. Teachers might be taking a certain classroom approach, such as the project-based learning approach, that they feel the parents would want to know about.