I have my Uni set to permafall, and until very recently, I made sure that all my sims graduated with 4.0s. On the other hand, I rarely make them skill as children or teenagers, and they don't deliberately skill all that much after Uni either. You can get a 4.0 without going higher than five skill points in any one skill, and that's often where my Sim's skills max out, unless they need them for promotion or roll up a want for something. (Or are Neat enough to love cleaning and do it autonomously.)

I don't have any hacks to make skilling harder, or anything like that. I do use the college clock to cut each semester shorter for all but one of my challenge families, since Uni is waaaaaay too long as is. And the challenge family usually has some Plot going on, so the first couple of years are usually just staging that around classes and the minimal skilling required to pass.

I don't think Uni has taken any of the challenge out of the game for me, but I guess it's a matter of differing playstyles.

I have a hack from here that shortens the semester time to 48 hours, and only let a sim skill when they roll a want for it. This combination makes it quite tough for many sims to get through college without at least getting an official warning.

I send all my sim teens to University. I use a shorter semester hack (48 hrs.), but otherwise have no rules, etc. for skilling, harder grades, etc. That said, I also never have my sims skill beyond what is required for the semester beyond what they do autonomously (working out and playing guitar is common). I avoid extreme skilling simply by having enough other fun things that they don't bother - bubblers, bars, large screen TVs

Grade inflation at Uni is rampant in fall, as just going to class and the final is usually enough to get a 4.0. However, you can easily lower grades in the other seasons by not going to class, not doing term papers, or (the big one), not going to the final - just like in r/l - party and sleep around instead. I find college invaluable for the sims, as it is where they make a network of friends and find spouses and/or lovers. It's rare for my sims to leave college without 15-20 friends and a fiancee in hand.

If you're finding the game too easy why don't you use SimPE to take away a bunch of skill points from your sims when they reach Uni just to make things harder for them, then do the same thing when they become adults so that it's harder for them to reach the top of their career paths? That's how I play and it seems like a better solution than using tons of hacks that are probably going to conflict with each other and mess up your game.

I am maybe only one who loves the Uni-time in campus I hated it while doing maxis universities but after Mootildas Brainania I simply loved the unitime And for my current hood I have made a very small uni-subhood, mostly 1x1 and 1x2 lots, small 3 person dorms and lots of communitylots of the size 1x1 My unistudents do not have time to actually study, they have so much other things to do as I do not give them much in dorms or houses, they simply have to be more outgoing (and as such as communitylot-addict as me it is great) :D

I apologize, little off-topic but had to mention that