In an exclusive sit-down with ET, Jon Gosselin says he's completely out of the loop when it comes to his 12-year-old son Collin's current whereabouts.

"I have an idea where he is but I don't really know where he is," Jon tells ET's Jennifer Peros. The former "Jon & Kate Plus 8" star goes on to say that while his ex-wife, Kate Gosselin, "says that Collin is in a special school for special needs kids with behavioral problems," Jon claims he has been told otherwise by law enforcement officials.

In August, Kate revealed that she enrolled Collin -- one of the divorced couple's eight children together -- in a program away from home to help him cope with "special needs." Collin is missing from the new "Kate Plus Eight" trailer that debuted late last month, and won't be appearing in the new season of the TLC reality show.

WATCH: EXCLUSIVE -- Jon Gosselin Talks Estrangement From His Kids -- 'I Haven't Seen All 8 of My Kids Together in 3 Years'

Kate currently has full legal custody of their kids -- twins Cara and Mady, now 16; sextuplets Aaden, Collin, Joel, Leah, Alexis and Hannah, now 12 -- while Jon has partial physical custody.

Jon, 39, says he hasn't seen Collin in over a year and a half, when he claims 41-year-old Kate took him out of the private school he was attending without consulting him. Jon says he's now going to court to attempt to get a judge to force his ex-wife to tell him where his son is.

"I mean, I ask but she doesn't tell me," he says about Collin's current whereabouts. "She doesn't answer any of my texts."

Jon claims that Collin's brothers and sisters are also not in touch with him, and also have "no idea" where Collin is. "They know that their mom told them that he has behavioral issues," he says.

As for whether Jon saw any behavioral problems with Collin himself, Jon says his son "seemed fine" to him the last time he saw him. He describes Collin as "really smart" and being "incredibly intuitive."

"I could see my kids getting annoyed with that because he's the smartest and he does this, and he does that, and he always wants it his way," he says. "He's very particular, which could be bothersome. But, he's very loving too. He was a cuddly kid as a baby."

ET has reached out to Kate for comment. Tune in to ET on Wednesday to see Jon go into detail about what he believes his kids' current lives are like with Kate.

WATCH: Jon Gosselin Celebrates Twins Mady and Cara's 16th Birthday With Sweet Instagram Pic -- A Few Days Late

In August, Jon told ET that he was very "upset" at Kate's headline-making tell-all to People, in which she discussed Collin's health. "Collin has special needs," Kate said. "[There's] a fairly fluid diagnosis of what those needs are, but he needs to learn certain strategies to help him deal with things. This has been a struggle we've had for a very long time, and it's one I've dealt with on my own."

"I love my children very much," Jon fired back. "I've always been there for them and I always will be. It's shocking."