NEW YORK - Enrollment is now open for the city's universal pre-kindergarten for this coming fall, but not without controversy. 

The free program kicked off last year as part of Mayor Bill de Blasio's plan to close income inequalities. It began with 53,000 children, but the goal is to boost that number to 70,000 through the participation of Jewish, Christian and Muslim schools. 

With the expansion to religious schools, some pre-K classes will be allowed to take a break during the day for non-program activities, such as prayer. Civil liberties groups are among those against the idea, saying that a prayer break in a publicly funded classroom may violate the constitutional separation of church and state. 

Another concern of religious communities is that most Orthodox Jewish preschools now have half a day of Hebrew learning, and in order for them to participate in universal pre-K, they have to accumulate a certain number of non-religious hours. Schools will be allowed to operate six days per week to meet the time requirements, but that means bringing 4-year-olds to school on the weekends. 

Children born in 2011 are currently eligible to enroll.