The blank page can be a pretty scary place. Staring at a blank page with the pressure to write something can make even the best writers' minds go as blank as the page too. If a child doesn't want to write, it is important to find that one defining reason why.
I once had a student who sat staring at the prompt refusing to budge no matter how positive, approachable or scaffolded the task was. After kneeling down next to him and asking him, "how can I help you?", he whispered, "I can't write here." Turns out the setting was unnerving him. His first composition was done lying on his tummy on the floor, away from the other students.
Here are some general hypothetical problems put together from my experience:
The reluctant writer who lacks confidence: These kids already THINK THEY SUCK no matter how hard they try. Don't correct their language. Pick out all the great things about their writing. Their ideas, style, even their handwriting. Praise them on how their writing reveals their character and how it's been a privilege getting a glimpse into their heads.
The perfectionist writer who cannot get started: These kids agonise over their introductions and have problems writing with a time limit. They often flunk school compositions in exams because they cannot put the pedal to the metal under pressure. Instead of writing whole stories, get them to write about short prompts. One paragraph will do. Tell them the first draft should't be perfect and it's okay to just flow through their ideas. They can edit and re-word things in their second draft.
The tongue-tied writer who cannot find the words to express ideas: These kids are brimming with ideas but struggle with vocabulary, spelling and syntax. They are the ones constantly asking for 'which word' or 'what's the spelling of' or 'how to say what-not'. As such, 2 paragraphs in and they're exhausted. You're exhausted. Start by having them show you a plan of what they want to write. Put together helping words and phrases they can use in draft 1. After they're done, pick out 2 key language areas they should work on, underlining specific mistakes. Get the child to draft 2 to try to correct these mistakes independently, then come to you for help if they cannot figure it out.
The artist / chatter-box / musician / scientist / athlete / dancer whose passions don't extend to writing: Ask the artist to add captions to their drawings, the chatter-box to record their story then transcribe the recording, the musician, scientist, athlete and dancer to tap into their passion and communicate it.
Writing is communication. It is connection. If children cannot see that they are making a connection with their reader, and their most important reader is you, no amount of drills or bribes or punishments will help.
Academic support for Primary 2