If a caster casts the same spell multiple times, only 1 concentration check is required. (for example, casting Invisibility on multiple allies). Some spells are considered similar enough to be lumped together for purposes of concentration. (Invisibility, Greater Invisibility, etc.)
NEW FEAT: School Concentration – all spells in the school are considered similar.
Note the prereq's for these feats have not yet been detailed. This one would a be high prereq feat.