From a brief survey of the CPS website, it appears that there are no cutoffs, other than the floors posted previously. Program slots are filled out of the applicant pool for each school/program, with several quotas, one based on pure rank, and then one for each of the aforementioned tiers. So the requirements change from year to year, and school to school.

I found these, for the Selective Elementary Schools (I think this means the Regional Gifted Centers):

The scoring system, up to a max of 900 points, based on NWEA, grades, and IQ. Notice that there is no distinction between 150 and 150+, and that the three criteria are essentially equally weighted:

http://www.cpsoae.org/Scoring%20Rub...Gifted%20Program%20--%202015-2016_v2.pdf

This is an interesting document, on the distribution of scores at different Selective Elementary Schools in the 2015-2016 applicant season. Some schools are markedly more selective than others:

http://www.cpsoae.org/Academic%20Center%20Cutoff%20Scores%202015-2016.pdf

Note that almost none of the students, including many of the top-scorers, in the school with the lowest selection scores would make it, even in the lowest-scoring tier, of the school with the highest selection scores. The highest selection school clearly had a number of students max out the rubric.

So some schools will probably be easier to get into, while others will have a higher likelihood of collecting high outliers.

...pronounced like the long vowel and first letter of the alphabet...