Preschools in the UK have curriculums they have to follow. That includes maths, reading and writing too.
I’m not going to comment on preschools in your country, but in the UK the kids who attended preschool are IN GENERAL the stronger students, socially, emotionally, and academically, when it comes to starting infants/ elementary school. Particularly in the less affluent areas. Though there might be some selection bias here too due to the kinds of parents who can sand their child to daycare verses those who cannot.