My 4-year-old is going into Transitional Kindergarten in a week. Cue the dramatic mom tears! Actually, as a former elementary school teacher, I'm thrilled with the idea. Schwarzenegger signed the Kindergarten Readiness Act into law in California in 2010, changing the enrollment date so that all kids would be at least 5 when they enter school here. The law also created Transitional Kindergarten (or 'TK,' which is often called Pre-K or PK in other states) to bridge the gap between preschool and kindergarten for students whose birthdays fall just short of the cutoff date. The idea is that older 4-year-olds need more mental stimulation than a typical preschool or daycare might provide, but they aren't ready for the full structure of kindergarten.