According to Official Guinness Records,
The largest maths class involved 3,611 participants and was organised by Mattecentrum and En Bra Start (both Sweden) in Gävle, Sweden, on 18 November 2015.The class took place in the Gävle ice hockey stadium and focussed on the Singaporean maths teaching technique.
For a complete list of 2015 records, please visit 2015 Guinness Records in Sweden.