Official sources said Paul Mohan, teaching at the Panchayat Union Middle School at Adailaiyoor in the district, allegedly placed the letter written in English, professing his love, inside the notebook of the girl a few days ago.
Another teacher had accidentally found the letter yesterday and brought it to the Head Master's attention.
Following a complaint from the Head Master, the Assistant Elementary Education Officer Palnivel issued orders today placing the teacher under suspension, sources said.