Transition from foam board to vinyl top (9')

Hey all; so just started learning to surf; have gone out maybe five times with group lessons on a big foam board and finally have been able to stand up and ride relatively consistently and once was able to turn and ride down The line. The surf school I'm taking lessons from encouraged me to try one of the vinyl top boards which are still long 9' but seem to have less float or a bit thinner and were described as having less of a rocker? Anyway I had the lesson today with it and I was wiping out all over the place. Almost every time I tried to stand up I pitched nose first and ate it. I was slipping and sliding off the thing even when paddling and just had a really tough time trying to get back to where I was on the foam board. I guess this is just to be expected?! Can some people just never get the hang of something closer to a real surfboard?? My goal is to longboard and I have to say today was a bit demoralizing.