If your unit of analysis is the student, then this will be a challenge. The reason is that Qualtrics records each "survey" completion as a single record. If you are observing multiple students, the only (clean) way to give them each a record is to enter them as separate surveys.
You can set up side-by-side items where students can be stacked. In that way, you can scroll up and down your list of students and record behaviors (or whatever you are observing) for each student as it happens. However, your data set will give you a column for every question for every student - which is kind of a mess to work with. Rather than being able to display student level info using the Report function or by bringing it into Vocalize, you will need to export it and transpose it (in SAS EG, we've had to transpose each item by student 1, student 2, student 3, etc.; , then append - to re-stack - the data set to get each "question" in a single column). (The same thing happens when you use the "looping" function in a survey).
Run some test data in the attached example survey attached to see what the data set will look like and decide if this is the best solution for recording your observations.
Example.qsfGood luck! (I'll follow this question in the case that someone has cracked it!)

https://www.qualtrics.com/community/discussion/comment/26630#Comment_26630Thanks. I'll look into this. I don't mind manipulating data outside of Qualtrics later on, if that makes the data entry task more user-friendly in the field. I do have a version of a classroom-level survey in which all fields for each observed student are in the same survey. An upside is that I can get to all students from within one survey. Another is that per-survey costs are reduced compared to having multiple surveys for multiple students. A downside is that I sort of have to decide on a max number if students to be observed per classroom.