The girl's post used language from a famous speech by Ho Chi Minh in 1946 appealing for resistance against French colonialists.
The post joked about never having to take exams again. The girl said the posting was "just for fun."
Vo Tan Dong, the deputy principal of the school in central Quang Nam province, said Tuesday that the girl deserved punishment, but the school allowed her to return because her family and the local Communist youth league had committed to "educating" her about her wrongdoing.
Ho Chi Minh is revered in Vietnam for leading the country to independence from French rule.