LEASES - Supplemental components of cash flow (Details) - USD ($)	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
LEASES
Operating cash flows from operating leases	$ 472,000
Financing cash flows from finance leases	71,000	$ 71,000
Total cash paid for amounts included in the measurement of leases	$ 543,000
Weighted average remaining lease term, operating leases	6 years 7 months 6 days
Weighted average remaining lease term, finance leases	5 months 1 day
Weighted average discount rate, operating leases	4.52%
Weighted average discount rate, finance leases	5.43%