This report is concerned with establishing a concordance between the regional PASEC and the international TIMSS and PIRLS achievement scales in francophone Sub-Saharan countries. the Rosetta Stone study consists of two assessment parts. The first part is the PASEC assessment including the PASEC context questionnaire. The second part is the Rosetta Stone assessment comprising test booklets with easier item blocks and passages from TIMSS and PIRLS. Both assessment parts were administered in three PASEC countries to the same students on two consecutive days. analyses were conducted using classical item statistics, item response theory (IRT) and population modeling. They comprise the evaluation of the data quality, evaluation of the psychometric quality of the instruments, establishing common scales across countries and assessments, and constructing concordance tables which account for the uncertainty of the measurement (measurement error).