I looked through all of your questions, and these abbreviations seem to have the relation to disabled children educational process - I've found all of them in the field-specific documents.
RT1 is more likely to be RTI: Response-to-Intervention (Model) - 干预回应(模式) http://www.cqvip.com/qk/82358x/201010/35504311.html
*The RtI is an instructional approach designed to identify struggling students and provide interventions explicitly targeted to meet their needs. https://lao.ca.gov/reports/2013/edu/special-ed-primer/specia...
RTC = Residential Treatment Center - 康复中心/住院治疗中心
*Education of Children & Youth Placed in Residential Treatment http://texaschildrenscommission.gov/media/83937/rtc-rt-repor...
IM = Mild intellectual disability - 轻度智力障碍
IO = Moderate intellectual disability - 中度智力障碍
https://data.cese.nsw.gov.au/data/dataset/specialist-support...