The changes will confine taxing subjects such as maths, French, history and science to the mornings while afternoons will be devoted to optional sports, cultural and artistic activities, road safety or health education lessons.
A pilot scheme was set up last September and effects of the revised timetable on about 100,000 pupils in 772 schools have been monitored.
The reform's supporters claim it respects children's biological rhythms and helps them work better.
Guy Drut, minister for youth and sports, announced the results of the evaluation last week at a conference of parents, teachers and educationists in Paris.
He called for the system to be introduced nationwide, and claimed the move had cut absence rates and led to a rise in the numbers of pupils taking school lunches.
He added that the afternoon activities are attended by nearly 100 per cent of pupils even though they are not compulsory.
He said behaviour both inside and outside school had improved.
However, he admitted it was not possible to judge if the scheme was raising pupils' academic performance "because it is very difficult to isolate the different factors which can have an effect - timetable organisation, teachers' methods and personalities, family attitudes and cultural environment".
He stressed that the reorganised timetable was in no case harmful to pupils' work.
M Drut, who claims support for the scheme from President Chirac, estimated that the measures could be introduced nationally over the next five years, an exercise that experts estimate would cost six billion francs (pound;660 million).
M Drut added the move would create between 50,000 and 70,000 new jobs, cutting unemployment costs and giving a boost to training courses in the sports and physical activities sector.
This plan is separate from the four-day week introduced in 1991. Traditionally, pupils have had Wednesdays off but instead have had to attend school on Saturday mornings.
Under the four-day scheme, increasing numbers of schools have opted to cut out the Saturday half-day, making up the missing hours by shortening school holidays.