The lords of the castle in the sixteenth and seventeenth centuries were the Ostrožič family, and they were Lutherans. Under them Ilava had an Evangelical school — a grammar school opened in 1560 — with teachers of real reputation, which in a small market town was unusual. This is the ordinary shape of the Reformation in Slovakia: the landowner's faith decided the parish's faith, so one family could make a whole valley Lutheran, and a century later another family could turn it Catholic again. Ilava's own turn came with the monks who arrived at the end of the next century.Hradnými pánmi boli v 16. a 17. storočí Ostrožičovci a boli evanjelici. Za nich mala Ilava evanjelickú školu – gymnázium otvorené v roku 1560 – s učiteľmi, ktorí mali skutočné meno, čo v malom mestečku nebolo bežné. Takto vyzerala reformácia na Slovensku úplne bežne: viera zemepána rozhodovala o viere farnosti, takže jedna rodina dokázala urobiť z celej doliny evanjelickú a o storočie neskôr ju iná mohla vrátiť katolíckej cirkvi. Ilava sa obrátila spolu s mníchmi, ktorí prišli koncom nasledujúceho storočia.
