After divorce, both spouses generally must support themselves if possible. With young children, at least one must provide care and cannot work full time unless third-party childcare is used. To offset the resulting income loss, the other must pay, alongside cash child maintenance, what is called childcare maintenance to compensate them.
The caregiving parent therefore need not work until the youngest child starts school and receives compensation. From school entry, 50% work is possible, from secondary school 80%, and from the youngest child's 16th birthday full-time work. Childcare maintenance must therefore be paid until, at the latest, the youngest turns 16.
In short: After divorce, former spouses should generally try to support themselves. Where children are under 16, the caregiving parent's employment opportunities are restricted and this loss is compensated. Once the youngest turns 16, that parent may reasonably be expected to work full time again.