The Ontario Education Quality and Accountability Office (EQAO) standardized testing starts on Tuesday and continues until June 3.
Students in grade 3 and grade 6 will be tested in math and on their writing and reading skills.
Last year, there were over 260,000 students tested across the province.
The results in 2017-2018 revealed that 61 per cent of grade 3 students and 49 per cent of grade 6 students were performing at or above the provincial standard.
The EQAO is an independent agency that conducts large-scale assessments to measure Ontario students' achievements in reading, writing and math.