I can only speak first hand about 2 schools that our children are at, the youngest are at a fondamentale, that's a combined maternelle (2 1/2 to 6) and primaire (6-12), the elder one has just started secondaire.
Our fondamentale is not particularly strict with negative discipline like detentions or sanctions, in fact I have never heard of it in our school, the children are expected to and appear in the main to do exactly as they are told. But from someone coming from the UK like I did, it does seem rigid in that the little ones keep to a routine of free play with parents until 9am, circle time, toilet, back to class for planned activity, morning snack, toilet, outside play, back to class for continuation of planned activity, lunch, sleep for youngest or outside play, then same in the afternoon.
I hear occasional shouting at children in class, but mainly the school is quiet and calm during lesson times - one of my best friends teaches maternelle so I often stay when other parents have gone to help her out and I volunteer during the lunch hour, so I get more of an insight than most other parents, I also know some of the other staff reasonably well. But this is MY EXPERIENCE, others may have not so happy experiences.
What do I hate about the school? Nothing except that it seems far too underfunded, even compared to other schools in the area.
What do I love about the school? Loads. The teaching staff are a great team, they unusually socialise outside work (Belgians don't often do this), they genuinely love their jobs and the children, are very motherly especially to the little ones.
Our kids absolutely love their schools, could not bear to remove them from where they are.