Formal writing prompts are writing tasks that require writers to think carefully before they respond. Specifically, they must go through the entire writing process, rather than just a sliver of it, before they are ready to respond.
For students grades 7-14, expository prompts that call for a formal response bear such names as essay topics, essay exams, term papers, research papers, or written projects.
In workplace situations, similar expository writing tasks ask for evidence-based memos, papers, reports, recommendations, or proposals.
In both school and work settings, formal writing should be authentic to the setting.
When writers have a formal assignment, they are supposed to come up with a response that’s logical and supported by evidence. Moreover, writers responding to a formal prompt are expected to take care with their spelling, wording, grammar and punctuation, and the appearance of their finished documents.
Except in exam situations, if writers don't have information they need to respond, they are expected to dig out the missing material before they turn in their work. (Typically students who attempt to remedy information deficits during an exam are not applauded for their initiative.)
For years most states identified topics appropriate for a particular grade and subject but typically failed to say what was essential for students to learn. The Common Core State Standards took the opposite approach, identifying essential skills students needed but leaving teachers to decide what topics would do the best job of helping their students develop those skills.
It's been my experience that whatever the official standards are, it's really classroom teachers who decide what’s important for students to know about (e.g. topics likely to show up on standardized tests) and which are essential for students to be able to use.
Experienced teachers know better than the suit-wearers at the state education department which of the 15,789 "required" facts, concepts, and skills really are essential for their students to master.
Teachers who use writing prompts to help them teach need to identify two types of essential information:
essentials for clear communication, and
essentials for their other course content.
As a rule of thumb, what's used regularly in everyday settings is essential knowledge.
The writing-related essential knowledge includes skills, concepts, and patterns:
Skills ordinary people have to use on the job, such as summarizing in a few sentences information they heard or read.
Concepts ordinary people need to know to improve their skills, such is the concept of verb tenses for those who want to improve their communication skills.
Patterns people have to recognize to perform their daily tasks, such as recognizing the main idea of a paragraph.
You already know what the writing essentials are, though you may not know that you know them. For example, you know that:
writing has a beginning (introduction), a body (middle), and a conclusion (ending);
related information should be grouped together;
evidence should be presented in ways readers will find convenient.
That sort of basic information is all you need to know to use formal writing prompts in your classroom.
(Incidentally, being able to spot essential information in written material is one of the essential writing skills you'll need to help your students master through your careful deployment of writing prompts.)
The other essential knowledge students will have to know is related to your course. It also will include skills, concepts, and patterns.
It's up to you to identify what the "non-writing" skills, patterns, and concepts for each class you teach. Fortunately, you only need to do the analysis once. Methods and strategies change, but the essential skills, patterns, and concepts of a discipline don’t change.
Hint: Start with skills. There are usually a relatively small number of them. Then figure out what patterns students must know to learn the skills; again, that's a relatively small number.
Finally, figure out which concepts students must learn before they can learn to recognize the patterns or learn the skills required in your discipline. There's absolutely no need to spend time presenting material that students can figure out on their own as they respond to your carefully crafted writing prompts.
It should be clear to you already that you need to exercise as much care when you prepare a formal prompt as you expect from your students when they respond to it.
Finally, I'll show you a way to use business writing to suggest to students who hate your course that it might have something useful for them. Here again you don't need to learn a bushel of new skills; you just use what you know.