if 28 students are too many for one 3rd grade classroom?

Depends on their abilities. Are there a lot of IEP students? Title students? Is there going to be other support staff to help?

yes!

of course I have a classroom of 12

I would add an aide.

YES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I freaked out when I started with 23 this year...had no room for the kids in my tiny room! (4th grade)

Many parameters can make affect that decision. ability of stdnts, tchrs, aides; amt of help from volunteers, physical size of room, & more.

Hee! "...can affect"

I think so

rough rule of thumb...grade level plus 20-K=20, 1st =21, 5th-25