AceShowbiz - Supermodel Heidi Klum's children are having a "hard" time keeping up with online schooling while staying with their mum in Germany, because the time difference means they are up late at night.

The runway beauty-turned-TV personality left Los Angeles and headed back to her homeland in October (20) to film season 16 of "Germany's Next Top Model", and she took her four kids with her after reaching a custody agreement with her ex-husband, singer Seal.

However, Heidi admits daughters Leni, 16, and Lou, 11, and sons Henry, 15, and Johan, 14, are having to get used to late nights to attend their virtual classes with the rest of their friends in L.A.

"It's very hard for them," she confessed to People.com. "When I decided this could be a possibility that I'm doing the show in Germany, I asked all my kids and I said, 'Is this something you guys are even up for? Because we will have to go for quite some time.' They all wanted to go because we've been stuck in the house."

"It's just a nice change for them, but it's definitely hard for them because they are doing school in a different time zone."

However, Heidi is grateful for her kids' teachers for making the most of technology to keep educating the youngsters.

"They're making all these things happen (so) that the brains of our kids can continue on learning and being those sponges that they need to be right now," she said.

Heidi also praised her children as "real troopers" for getting on with their schoolwork despite the late nights.

She added, "It's hard because they do it here late at night, until like 11pm at night, because they actually are doing school on L.A. time still with their class. So kudos to my kids for not slacking and doing it all. They're real troopers."