On research papers based on questionnaires

My second bad feeling about some papers is the use of students in questionnaires about learning method evaluation. My First Assumption is: students always lie. Participants' feedback is always too high. No one will ever tell you are completely wrong in doing your work, if you play a role hierarchically higher than every particiant's, as teacher role is, whatever pedagogical framework you actually use.

Corollary: do not base your research only on student-based questionnaires. And please provide a control group! This is sociological basics!