You don't always have to use "ada," you can also just say "dia di sekolah." It's the same thing. You should know that, Duolingo.
Hai! Many sentences in the course can be accepted with "ada" and "berada", those verbs are lacking in the most of sentences. So, I think the contributors already know "that". Please, try helping with the course reporting your sentence.
Selamat belajar! :)
This sentence can be, "Ia ada di sekolah."
I think it's will be more correct if you use Dia instead of Ia
Yes, commonly we're using Dia rather Ia, but Ia is acceptable CMIIW