Will this laptop run the sims 3 smoothly and on high graphics

I think that one gets a definite "probably" as far as TS3 goes.

The GTX 950 is the lowest within that series of what we would tend to call "fine" for TS3 and all EPs. But the 950M is the mobile version and isn't quite as strong. The very highest of graphics settings may still be okay, not counting water/reflections and high detail lots as we always advise not running those two at the highest on most systems. Or you may need to dial things down a bit. Experiences with a card just on the edge like that are going to vary, also depending on player play styles, expectations, and if all EPs are really going to be in play all of the time but especially Pets and Seasons.

But this laptop is probably around 5 years old already. Unless it's been sitting in a box for that long, I would be more concerned that its components might not be performing as well as they once were especially when it comes to its cooling system. Course work is not likely to tax its performance very much, but sims games can. Again everything might be fine, but there are always risks with used hardware that the unit may not have as much life left in it as one might be hoping for and there really isn't going to be any recourse as there might be with a new system that might come with warranties if it starts failing far too soon and if it does so that could potentially affect your ability to use it for classwork and other more routine purposes.

I take it that a new system is totally out of reach, financially, as would be keeping an existing one for playing on but acquiring what I assume is a lighter weight one for portability?