REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
REVENUE RECOGNITION [Abstract]
Unearned tuition	$ 22,183		$ 22,183		$ 23,453
Revenue recognized included in contract liability			22,400
Disaggregation of Revenue [Abstract]
Total revenues	80,464	$ 62,470	158,461	$ 132,511
Services Transferred at a Point in Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	6,348	2,977	11,200	6,549
Services Transferred over Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	74,116	59,493	147,261	125,962
Transportation and Skilled Trades Segment [Member]
Disaggregation of Revenue [Abstract]
Total revenues	56,965	42,915	112,636	91,971
Transportation and Skilled Trades Segment [Member] | Services Transferred at a Point in Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	5,065	2,038	8,585	4,536
Transportation and Skilled Trades Segment [Member] | Services Transferred over Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	51,900	40,877	104,051	87,435
Healthcare and Other Professions Segment [Member]
Disaggregation of Revenue [Abstract]
Total revenues	23,499	19,555	45,825	40,540
Healthcare and Other Professions Segment [Member] | Services Transferred at a Point in Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	1,283	939	2,615	2,013
Healthcare and Other Professions Segment [Member] | Services Transferred over Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	$ 22,216	$ 18,616	$ 43,210	$ 38,527