Le garçon a chanté toute la nuit. The boy sang all night long.
Les filles ont chanté toute la nuit. The girls sang all night long.
In the second sentence, even though the subject is feminine plural, the past participle is the same as in the second sentence where the subject is masculine singular.
In this lesson we will see that in some cases the object -not the subject- agrees with the past participle of the verb with the auxiliary “avoir”, but there is a condition for that.