An open-class notice (授業参観, jugyō sankan) is the visit the Ministry
of Education's school guidebook describes: parents come to school and
see the lesson and how the child is getting on. It is often paired with
a class meeting (学級懇談会, gakkyū kondankai), where parents and the
class teacher exchange information about school and home.
The guidebook puts the example in the first term and says the timing
differs by school. The paper names the date, the periods, and anything
you should bring, such as indoor shoes. Reply if the paper asks you to.
Verify the day with the school.
Your child's dates, not the general ones
Add your child and ward. The timeline does the rest.