Ave Andrew,
I'm afraid you have misunderstood the way the "rate" question works in questionnaire. It will certainly not enable the respondent to rate only 5 out of 25 possible choices. It can only enable the respondent to put 25 items in order of preference.
You should use the Check boxes question type, making sure to set both Min. forced responses and Max. forced responses values to 5. If a student submits their responses with less or more than exactly 5 choices, an error message will be displayed.
See attached screenshots.
Hope that helps,
Joseph