AceShowbiz - Katharine McPhee and David Foster have disagreement over how to discipline their son. The 39-year-old singer and 74-year-old music mogul share son Rennie, two, together and Katherine admitted that their large age gap has led to very different views on how to parent their child.

"I want to start disciplining [Rennie] and Kat's not really down with that," David told PEOPLE. Katherine replied, "No, that's not true. I just want to discipline in my own way."

"There's the more old-fashioned way of disciplining which involves time-outs and things like that. My take is that you can have more mindful parenting opposed to just assuming that a two or three-year-old can have time alone to reflect on what they've done poorly."

"I think the more new way of parenting is understanding that with a child, there's only so much that they can intellectually understand. Saying 'That was really bad, that was really, really bad,' gets into a shaming thing. I think disciplining is something that happens over time."

However, David - who has five grown-up children - doesn't quite agree. Katherine said, "David's more results-based. He's like, 'He can't just walk by and swat people.' Of course not. But he's two and a half and he's learning those things. It's just a different approach. I think his era of parenting is different than mine. We don't have arguments about it."

"They learn how to how to have personal space and all those things over time. They have to have experiences where they have negative reactions from people more than just their parents, from teachers and fellow students. They get to experience it with life. So we'll just wait. Talk to us when he's three."