I send mine to nursery/preschool since 3 months old.
Now my daughter is 6 and next year will graduate from the school and go to primary 1.

Go do site visit before deciding, check on the teacher vs kids ratio. Then if possible talk to other parents with kids there to see what's their opinion.

The school my daughter went charge us around 2.5k per month. From morning till 6pm.

Only registered person can pick up the kids and got apps that will notify you when kid go into and out of school with pictures. If not the registered person want to pick up the kid the school will call the parents/guardians first to confirm.