How to know if student films should appear as credits on an actor's CV
Simply put, yes! The fact of the matter is that the more acting work you have done, the more likely a casting director, producer, or director is to invite you to audition for their project.
As a professional filmmaker you might not be willing to take a chance on someone who has never been hired as an actor. However, if they see that you have been hired for all kinds of different projects it immediately tells them that you most likely are a good actor. This in turn tells them that they would at least not be wasting their time, were they to invite you to an audition. Moreover, they can tell by looking at your CV that you've been proactive in building your career by taking part in different productions. These are both paramount qualities an actor needs to have.
Furthermore, acting in student films provides you with more showreel material - something potential employers are always looking for. If you do not have a showreel you risk not being considered for a part simply because watching an actor's showreel is a quick and simple way of determining whether or not he or she would be suitable for a specific part. And because it is not a good idea to include material in your showreel that you haven not listed in your CV you need to make sure you have added all your film credits to your CV.
Casting directors hate wasting time which is why it is important to make sure they are able to access all information on what you have done so that they will be interested in auditioning you. Lastly, student films are not only great for practice but they are also brilliant for making connections so make sure you audition for and take part in as many as possible.