REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
REVENUE RECOGNITION [Abstract]
Unearned tuition	$ 24,691		$ 24,691		$ 23,453
Revenue recognized included in contract liability			22,600
Disaggregation of Revenue [Abstract]
Total revenues	89,059	$ 78,792	247,520	$ 211,303
Services Transferred at a Point in Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	7,821	6,986	19,022	13,535
Services Transferred over Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	81,238	71,806	228,498	197,768
Transportation and Skilled Trades Segment [Member]
Disaggregation of Revenue [Abstract]
Total revenues	64,950	56,828	177,586	148,799
Transportation and Skilled Trades Segment [Member] | Services Transferred at a Point in Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	6,203	5,520	14,788	10,056
Transportation and Skilled Trades Segment [Member] | Services Transferred over Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	58,747	51,308	162,798	138,743
Healthcare and Other Professions Segment [Member]
Disaggregation of Revenue [Abstract]
Total revenues	24,109	21,964	69,934	62,504
Healthcare and Other Professions Segment [Member] | Services Transferred at a Point in Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	1,618	1,466	4,234	3,479
Healthcare and Other Professions Segment [Member] | Services Transferred over Time [Member]
Disaggregation of Revenue [Abstract]
Total revenues	$ 22,491	$ 20,498	$ 65,700	$ 59,025