To favour secondary school performances of low achievers, it could be advisable to change teaching either from primary level, to help pupils to enter secondary school or at secondary level to back up the adjustment of less able pupils. We can endeavour to modify endogenous variables affecting learning process. Among these, time provision between various activities at both primary and secondary levels, is an especially relevent factor. To favour secondary school performances of low achievers, it could be advisable to change teaching either from primary level, to help pupils to enter secondary school or at secondary level to back up the adjustment of less able pupils. We can endeavour to modify endogenous variables affecting learning process. Among these, time provision between various activities at both primary and secondary levels, is an especially relevent factor. The present study based on a sample of one thousand pupils in the last year of primary school (with a follow up study in the first grade of secondary school) is an attempt to show the heterogeneity of school time use especially in primary grades and to understand why. It is an analyse of short time and long time effetc of this diversity on pupils' progression differences.