The show is somewhat similar to JK Rowling's books. Let's make a comparison:
There are three main protagonists in "Casper's Scare School" : 2 boys and 1 girl. There are three main protagonists in the Harry Potter books : 2 boys and 1 girl.
The students in "Casper's Scare School" go to a strange school with gargoyles, awkward teachers and so forth. The students in in the Harry Potter books go to a strange school with gargoyles, awkward teachers and... you get the picture.
The main character in "Casper's Scare School" is kind, friendly, with a family that doesn't understand him and he's dead. The main character in the Harry Potter books is kind, friendly, with a family that doesn't understand him and he's alive (for now).
Ra is Casper's best friend (besides Jimmy), always in his shadow, not as interesting as he is and lazy about schoolwork. Ron is Harry's best friend, always in his shadow, not as interesting as he is and lazy about schoolwork.
Mantha is also Casper's friend. She is very calm...zombie, who is tight with her friends, just la Hermione is. Except the zombie part.
Thatch and Draco are the antagonists playing the part of the school bullies. Both are cruel, selfish and whatever you can think of.
Well, that's really original. What will they think of next? Two midgets who have a ring and must toss into the Eternal Soup of Fire, being guided by a bald eagle who yells 'My precious'?
At least the design and mimics of the characters are pretty good. The voices are not bad, especially Casper's. Enjoy watching it!