Checks were carried out at 39 minority schools, with 25 of them in the countryside and 14 in the Latvian capital Rīga, VVC rep Ingrīda Bērziņa said.
Out of 1,451 teachers whose language knowledge was examined, 143 were fined, or about 10%, Bērziņa said.
The fines handed to the teachers range from €35 to €280. VVC say the situation has improved over the past few years.
"I think that in some way it is aided by the generational change, so to speak. As the teachers born after 1980, the younger ones, have considerably less problems with the use of the official state language, as they've been educated in Latvian. Meanwhile teachers in the middle age and older do have some trouble," said Bērziņa.
However the center says it had expected faster improvement after the 2014 and 2015 language examinations.
The Education and Science Workers' Association (LIZDA) however thinks that there hasn't been enough support for teachers to learn Latvian.
Its head Inga Vanaga does admit teachers have access to language classes. "In essence, this support arose when we started talking about it in louder tones and the ministry understood that people won't be spending their own money to attend these classes," said Vanaga.
The State Language Agency, which provides teachers with language classes, disagrees. "The support has always been there. Maybe the public at large hasn't, but schools have been in the know," said Dace Dalbiņa, an official at the agency.
She pointed out that the agency has been supporting the teachers from as early as 1996. "In sum the state has offered free classes that [..] have been attended by more than 19,000 teachers," she said.
The agency also has funds to ensure education for 8,000 more teachers. Last year, about 550 attended such classes but the number is expected to rise to more than 1,000 this year.
Last March, the Latvian parliament voted through legislation which raised the number of classes taken in Latvian at minority schools from 40% to about 80%, with all core subjects taught in Latvian from September 2019.
In response to the reform, VVC has stepped up the examinations of teachers' language ability and will continue to do so, VVC told Latvian Radio.
The fines have been issued at a time when teachers' wages are a contested topic as teachers are considering protests during exit exams to have their wages raised.
The minimum salary for teachers is at €710 per workload (30 hours per week), which the Swedbank wage calculator for 2019 puts as €532 after tax (it can be higher if the teachers have dependents). The average net wage in Latvia was €742 last year.