Two things in a Japanese school day surprise families who are new to
them. The Ministry of Education's guidebook for foreign children
describes both as the usual pattern.
Cleaning
Students share the cleaning (清掃, sōji) of the rooms and the grounds
they use. A class note that puts your child on cleaning duty is asking
for that share of the work. The guidebook does not name a fine for
missing it. If the child cannot do the day, tell the class teacher.
Clubs
Children who want to can join a sports or culture club (部活動,
bukatsudō) after school. The guidebook says it is for those who wish
to. It does not say every child must join, and it does not name a fee.
The school's own club note is the one that lists days, kit, and cost.
Elementary schools more often have a shorter after-school group than
this junior-high style club. The ward's after-school childcare club
(学童) is a different application, for working parents, and is not this
club.
Your child's dates, not the general ones
Add your child and ward. The timeline does the rest.