Agree with Kathryn. If its not you grading them, then let someone else make the decision. If they aren't good enough, they won't pass. And if they do pass, you have to ask about the association you are with. Do you have different standards? If you don't think they are ready but the committee does, well, who's right?
If they fail, maybe this will make them re-evaluate their training and their approach to it.
As to starting another system... it depends why you are doing martial arts in the first place. Personally I don't like much of the Ju Jitsu in the UK. Very little of it is Japanese for a start. Not to sound like a Koryu snob, but if an association is going to give itself a Japanese name and infer they are teaching traditional Japanese fighting arts (which many Britisih JJ associations claim they are as part of their marketing) they should have a background in traditional Japanese systems. Sadly many do not.
Additionally the training can be, for me, quite dull. Endless compliant partner drills is the order of the day in many places. There are some classes that now offer a bit of sparring or are going down the sports Ju Jitsu route.
Although many RBSD like Krav Maga and Defendo also use compliant drills to a certain extent, they at least make an attempt to deal with other factors of modern day self-defense, including trying to replicate psychological conditions of confrontation outside of class. Many JJ classes in the UK have nothing like that.
I've known an experienced WJJF student who got beaten up quite badly in an attack outside a pub (had to recieve hospital treatment), and have seen a WJJF 2nd Dan getting submitted by a BJJ white belt in a grappling tournament. If you want to study Ju Jitsu because you might like it, go for it. If you are looking for a practical fighting or self-defence system, or to study the traditional fighting methods and culture of Japan, I recommend you look elsewhere.
"Let your food be your medicine, and your medicine be your food"