«Мои дети ходят в школу» means ”My children attend school”. This is simply the way you say “to go to school” in Russian.
If you want to stress the fact that they walk (on foot), you can say «Мои дети ходят в школу пешком.»
If you want to have a continuous feeling to your sentence (as if they are en route to the school), your best option is «Мои дети (сейчас) идут в школу».
The point here is that ходить supposedly means "to go by foot", which in English means "to walk", so that ходить в пешком would literally mean "to go by foot on foot".
In one exercise, people were marked wrong for using идти instead of ехать because the distance was inferentially great, so that walking would not be likely. Duo was being very precise there.
But here, where ходить seems to be a multi-directional version of идти, we find that "on foot" isn't relevant. There seems to be a logic problem there.
My kids walk to school was added, actually.
A bit a clarification: the sentence in the title does not suggest that children are walking to school instead of going there by bus (unless they travel to school that is, like, in another state). Ходить and идти are commonly used for your trips within town—to places like work, school, a store, a museum or attending some classes and events, all regardless of how exactly you get there.
In this sense, the use of идти/ходить with школа, работа or концерт will not be the same as with a random place name (to be on the safe side: I mean a concert somewhere nearby).
идти is also used when talking about public transportation and routes (in fact, the common end of line announcement in Moscow Metro ends with "Поезд дальше не идёт, просьба выйти из вагона.").
By this logic, why was "Yes, my children attend school" rejected as incorrect?
I also have a request: Please, don't use Russian italics. It's hard enough reading Cyrillic in regular font, especially when Italic т = т which looks like English m.
this should be accepted. russian doesn't have a continuous tense, so it shouldn't differentiate it from the simple. i've seen these tense problems all over the course. instead of getting mad, just chalk it up as a chance to squeeze in some more practice. :)
However, there is a difference in this case: "are going" would be «идут»; «ходят» describes a habitual action, not something that is happening right now. I'm not sure what's the grammar rule on this, but as a Russian native, I'd say you cannot translate it as "my children are walking to school".
Later edit: look up verbs of motion, unidirectional vs. multidirectional.
that's very interesting. i hear the word 'сейчас' so often, i had no clue some verbs behaved like this. thank you.
Thank you so much for clearing this up. It has been bothering me all night.