I'm not totally sure on the acuracy of all of these, but here are a few RIT/MAPS score to lexile conversion charts I found:

http://www.ode.state.or.us/teachlea.../summerinstitute/2006/ritlexiletable.pdf

http://mapregionmtg.wikispaces.com/MAP+and+Lexile+Chart

http://www.esu1.org/downloads/virtuallibrary/RITtoLexileReport.pdf

From what I'm seeing a reading RIT/MAPs score of 170 would correlate with a basal/beginning reader level in the Lexile framework, which should be below 100, I believe.

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