A Book from my Childhood

For a long time, I've been thinking about a book I read when I was younger. It was years ago - I was still in school, must've been, god, fourth or fifth grade. I only remember bits and pieces, but I don't think I was able to appreciate it at the time. I was a retarded kid.

Anyway, was hoping maybe some 4channer may have read it at one point.

The main story was about a bunch of kids who joined an Academic Challenge-type team. The early chapters were dedicated to each kid doing something different the summer before [ I THINK ].
One of them wrote invitations for a wedding.
When they were at school, there was a foreign student who made friends with them by sending them cryptic messages via library books. I think they were Alice in Wonderland references. They all eventually had a tea party at his house.

I know, sounds like a great book. Excitement abound. </sarcasm>

Anyone know the title of this thing?

Wow, I remember having to read that in gradeschool as well.  Sadly, I cannot remember the name.  It was actually a pretty decent book considering the age group that it was aimed at.

However, from my memory, I can tell you that there plenty of better books to read after you pass the 5th grade reading level/level of life experience.