"I wanted to know who had helped the students."
Translation:Ik wilde weten wie de leerlingen had geholpen.
The translation to Dutch gives the question a different meaning....ie
...who had helped the students turns into
who the students had helped
Yes, it is confusing. The conjugation "had" tells you that "wie" is the subject of that relative clause, not "de studenten" (which is plural).
- Ik wilde weten wie de leerlingen had geholpen. = I wanted to know who had helped the students.
- Ik wilde weten wie de leerlingen hadden geholpen. = I wanted to know who(m) the students had helped.
Because the verbs in a subordinate or relative clause are always pushed to the end, these two sentences use the same word order (unlike in English).
I've added it, thanks. For the record: "wou(den)" is an informal alternative to "wilde(n)".