ACQUISITIONS - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill	$ 1,727,852		$ 1,481,725	$ 1,431,967
Only About Children
Business Acquisition [Line Items]
Cash	4,705	$ 4,705
Measurement period adjustments, Cash	0
Accounts receivable and prepaid expenses	4,376	4,295
Measurement period adjustments, Accounts receivable and prepaid expenses	81
Fixed assets and technology acquired	20,749	21,702
Measurement period adjustments, Fixed assets	(953)
Goodwill	286,619	283,466
Measurement period adjustments, Goodwill	3,153
Intangible assets	27,568	30,945
Measurement period adjustments, Intangibles	(3,377)
Operating lease right of use assets	155,256	156,678
Measurement period adjustments, Operating lease right of use assets	(1,422)
Total assets acquired	499,273	501,791
Measurement period adjustments, Total assets acquired	(2,518)
Accounts payable and accrued expenses	18,240	17,991
Measurement period adjustments, accounts payable and accrued expenses	249
Deferred revenue and parent deposits	6,778	6,809
Measurement period adjustments, Deferred revenue and parent deposits	(31)
Deferred tax liabilities	0	3,392
Measurement period adjustments, Deferred tax liabilities	(3,392)
Operating lease liabilities	161,969	161,405
Measurement period adjustments, Operating lease liabilities	564
Other long-term liabilities	5,550	5,458
Measurement period adjustments, Other long-term liabilities	92
Total liabilities assumed	192,537	195,055
Measurement period adjustments, Total liabilities assumed	(2,518)
Purchase price	306,736	$ 306,736
Measurement period adjustments, Purchase price	$ 0