I know Degrassi can be sappy and over-the-top, but I love it anyway. My mom introduced Degrassi Junior High to me when I was 14, and since then, I've been a fan...
I'm fairly new to typing, so be easy on me if I'm really off.
I need to rewatch Degrassi Junior High and High, but here are a couple:
Joey - ENFP or ESFP
Caitlin - INFJ
And ones I'm fairly sure about for Degrassi: The Next Generation...
Emma - ENFJ
Manny - ENFP or ESFP
Toby - INTP or INTJ
Sean - ISTP
Liberty - ISTJ
Paige - ESFJ
JT - ENFP or ESFP
Ellie - INtP or INfP
Jay - ESTP and awesome
Alex - ISTP
Peter - ESTP
Clare - INFJ
Holly J - ENTJ
Sav - ISFP
KC - InfP, although he's tricky to type
Connor - INTP or INTJ
Declan - INTJ
Wesley - INTP
Eli - same as Ellie, INtP or INfP
While I happen to have just recently registered for these forums a few minutes or so back, I must say nonetheless that, as an avid fan of the Degrassi series myself, I must say I agree with each of your types for the characters, although Sav's truly surprised me, since I'd never quite thought of him as being ISFP before although I can see him as one now that i think of it. As for other characters you didn't type yourself:
Hazel (Paige's best friend/ side-kick throughout the earlier seasons)- ESFJ
Ashley- classic INFJ 4w5.
Rick- INFJ, although quite an unhealthy one at that.
Terri- ISFP or INFP
Spinner- ESTJ
Jane- EnTP?
Kendra (Toby's crush and girlfriend throughout the earliest seasons, also Spinner's adoptive sister)- INTp
Anya- either ISFP or EnFP.
Craig- an unhealthy ISFP.
As KC himself, he is tricky to type initially, yet nonetheless, he seemed to make rather brash decision making on the basis of his, often unstable, feelings in the moment and seemed to likewise live in the present without much outward look towards the future. He appeared to be swayed rather easily by emotions connected to the now as well, and seemed to have more so interests upon things involving in the senses as well as self-expression if anything. Craig also didn't strike me as being much of an extrovert at all.
Jimmy Brooks- ENFJ.
I see him as being such due to his having seemed to be rather outgoing and extroverted while still seeming that all around nice guy likewise that everyone seemed to care for, and the way in which he handled the situation after finding out Spinner's involvement with the shooting made me feel he was more so projecting that certain type of intense and downright punitive shunning ENFJs are said to display when really angered or offended by something in particular.
Marco- INFJ or ISFJ
Darcy- ENFJ
Alli- ESFP
Way too motivated by her own feelings at times to seem as much of a Ti user at all, although I used to see her more as ESTP when she first appeared in season 8, and she certainly seems to live in the present moment as well.
Bianca- ESTP
Jenna- ESFP
Fiona- iSFP.
May be ESFP as well, and yet I see her slightly as being more introverted and motivated by her Fi for some reason than her Se, particularly seen with how she reacts initially towards Holly J. and Declan's past relationship as well as how she seems to be constantly motivated more so by what she is feeling within than what occurs externally. Once more, another slightly unhealthy ISFP.
Johnny DiMarco- ISTP
Riley- ISfJ?
Zane- ISFP
Adam- either INtP or INfP
Leia- underdeveloped
I see Manny as being more ENFP than ESFP, although, since she seemed slightly more imaginative as well as romantic, particularly where it concerned love, than a sensor would be, and appeared to have that natural sort of zesty bubbliness I feel an ENFP would have within as well. I truly feel, although, that JT could have been either type and really have a bit of trouble granting him one of the other in specific, although still I'm fairly certain he most probably was an ExFP of some sort, and that Eli, more recently, seems to be leaning more so on the INFP side as he appears reveals more of his vulnerabilities towards the audience than INTP. I agree on Wesley's being an INTP as well, and feel Toby is the same type as well.
Even though I realize Degrassi can appear over-the-top and melodramatic as you stated as well, I nonetheless just love this series and literally have watched each episode from the first 9 seasons (although I caught up admittedly on some of the seasons due to a marathon that was on Teennick last summer...).