What is the longest length of mandatory secondary school?
CREATE TABLE table_1831309_1 (length_of_mandatory_secondary_school INTEGER)
SELECT MAX(length_of_mandatory_secondary_school) FROM table_1831309_1
### Context: CREATE TABLE table_1831309_1 (length_of_mandatory_secondary_school INTEGER) ### Question: What is the longest length of mandatory secondary school? ### Answer: SELECT MAX(length_of_mandatory_secondary_school) FROM table_1831309_1