In reality, it is up to each individual teacher to insure that multicultural education holds a place in his or her classroom. According to the US Department of Education, there are 3.1 million teachers employed in the United States. It would be impossible to even guess at how long it would be to insure that each and every teacher taught religion and spiritual diversity in the multicultural classroom.
Thus, it would be very difficult to define a universal time-line which sets the "cut-off" for multiculturalism to be mainstreamed into every classroom. Problems associated with this are classrooms, or communities, which do not support multiculturalism. In some of these cases, fault does not lie with the school refusing to include multiculturalism in the classroom. Instead, the school's population is singular in ethnicity. In this case, no students exist within the school's population to promote a multicultural education. In other cases, as sad as it is, some schools do refuse to accept ideologies outside of their own.
A solution for insuring implementation of a multicultural in every school would be to amend the Common Core to include studies in different cultures, religions, and ethnicities. Unfortunately, just because a new national curriculum demands changes does not mean that every school will comply with it. Essentially, there is no overseeing "entity" which assures that specifics of the Common Core are taught.