The Perfect Passive System
The perfect system of all conjugations is formed by the combination of a form of esse (perfect: sum; pluperfect: eram; future perfect: erö) plus the fourth principal part - the perfect passive participle. You translate the Latin perfect passive using the English perfect passive (the perfect of the linking verb "to have" or "to be" plus the passive participle).
The perfect passive participle, like all participles, is an adjective - therefore, it must agree in gender, number and case with its subject., e.g.:
You will be tempted to translate the perfect passive as though it were a present passive because the perfect passive is formed with sum (i.e., the present tense of esse). RESIST this temptation - in the perfect passive system esse and the perfect passive participle work as a unit. When you have both parts of the unit you are in the world of the perfect passive system and must translate with a perfect of "to have."
e.g.: puerï sunt laudätï - the boys have been praised/the boys were praised
do not translate this "the boys are praised" - which would be puerï laudäntur