Visiting an elementary school
Preschools take their students to visit a variety of places and facilities, and you may write about your child's reactions after one of these visits. You may of course speak to the teachers directly instead of writing in the renrakucho. In this scenario, the nencho (third-year) children have visited an elementary school.
Since these visits are school events, you are not obliged to thank the school for them. However, if you feel that the teachers really made an effort on behalf of your child, you may of course choose to express your thanks.