child support is your HALF of the childs expenses. ANd in Ma. unless otherwise noted, that includes extra-curicular activities In a sense you are reimbursing the mother for money all ready spent. how do you know she is not spending it on your daughter? once the child support is in her hands it co-mingles with the rest of her finances.
but once it leaves your hands it is up to the receiver to decide how it is spent. if she decides to use the whole thing on the rent, or even go to the mall that is her choice.
Maybe if mom does not want to swim, maybe you could join the Y and take your daughter yourself?
"It is easier to build strong children than repair broken men." Frederick Douglas