The irony of pedagogy
In his time, Locke was surrounded by pedagogies that had to do primarily with children's bodies and bodily behavior. Locke saw that, actually, children were governing themselves through a sense of justice, and that by educating them on the proper practices of self-denial and open-mindedness, a child's soul could be made healthy. This may not seem ironic now, but that's because Locke's philosophies are engrained in our perspective in the West, but especially during Locke's time, this idea was perplexing.
The irony of implicit biases
Look at what the 'Tabula Rasa' idea means for inherited ideas. Instead of taking responsibility for their beliefs, parents and pedagogues can sometimes make the mistake of teaching an idea to an impressionable kid as if it's obvious. That means that a child is given a set of implicit biases, and the irony is that it feels true and essential, but it's not. When that child grows up and passes along those same ideas to their own children, it will feel obvious and objective, but it's not. It's still just unfounded bias.
The irony of sheltering or privileging a child
Locke saw the dangers of the dominant pedagogical view of his time, one that he felt was sparing children from difficulties. He said this would make them have problems adjusting to adult life, since they weren't taught to deal with difficulties and discomforts. Ironically, treating a child with extra love and consideration might be harming them in the long run.
The irony of human belief as a construct
Instead of viewing human belief as an issue of religious truth, Locke just details the mechanisms that children employ for making sense of the world, offering a point of view that flew directly in the face of the kind of rationalistic approach to child-rearing. What feels like moral duty might actually amount to indoctrination and closing children's minds. In other words, there is an irony at the foundation of a human's ability to 'believe,' because of the way beliefs shape a child's sense of self.
The irony of gender.
Ironically for his time, Locke saw past gender as a meaningful difference among children. He doesn't feel like he needs a second chapter of this treatise to talk about women. He just assumes that men and women have these essential qualities in common. That's very forward-thinking for the 17th century.
