You definitely have a great vocal range and it seems like you specialize more so in cartoony voices than realistic voices. Your acting is pretty good too. However, my biggest criticism of your demo is the majority of your clips are way too brief and lack character. A lot of these felt like throwaway one-liners with just voices attached to them.
For example, your "Still a strict teacher huh?" clip lacked any kind of depth. Who is the character talking to? What's the context? I'm not saying these have to be full blown monologues or anything, but part of acting is building believable characters and unfortunately after I listened to your demo a couple of times I didn't walk away remembering any of what I heard.
Next time try to work more on creating entertaining characters and dialogue your audience can sink their teeth into. Instead of a collection of 3 - 4 second clips, try to aim for 7 - 9 second clips. Use that time to flesh out your characters and make them mean something to you. That doesn't mean you have to change up the style of your characters, but give them purpose and more to say. By making the clips longer it also means you don't have to have as many characters. 10 characters should be enough and this allows you to cut the fat on your demo and trim down your time. People have short attention spans and if your demo is longer than 90 seconds it may not get listened to.
I hope none of this sounds harsh. I'm not trying to demoralize you, but give you some honest critique to help. We voice actors need to help each other get better and call each other out when we feel like one of our peers isn't giving it their best. I like your work on the College Off the Record series and I actually would have loved it if you had put a clip of J on this demo. You have great potential man, but it just needs to be honed. I'm still trying to get there myself. Good luck and I hope all this helps!