Increasingly, schools are fencing off a (usually grassy) play area for the kindergarten kids. This is a very sensible move for multiple reasons: it contains them, it protects them to some degree from balls that are thrown or kicked by older students, it prevents access by unauthorized persons, etc.

Fencing an entire school property is usually not possible for reasons of cost, fire regulations, school bus access, etc. Fencing a small K-yard is an affordable & prudent investment.