Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Apr. 30, 2019	$ 9,164	$ 56,831	$ (2,111)	$ (841)	$ 46	$ 63,089
Balance (in Shares) at Apr. 30, 2019	9,163,940			183,661
Contribution of stock to 401(k) plan		236		$ 181		417
Contribution of stock to 401(k) plan (in Shares)				(39,403)
Stock-based compensation expense		304		$ 8		$ 312
Stock-based compensation expense (in Shares)				(1,850)
Exercise of stock options and stock appreciation rights - net of		(457)		$ 457
Exercise of stock options and stock appreciation rights - net of (in Shares)				(99,712)		171,250
Other comprehensive income (loss), net of tax					444	$ 444
Net income (loss)			(10,026)			(10,026)
Balance at Apr. 30, 2020	$ 9,164	56,914	(12,137)	$ (195)	490	$ 54,236
Balance (in Shares) at Apr. 30, 2020	9,163,940			42,696		9,121,000
Contribution of stock to 401(k) plan	$ 26	325		$ 68		$ 419
Contribution of stock to 401(k) plan (in Shares)	26,192			(14,926)
Stock-based compensation expense	$ 4	269				$ 273
Stock-based compensation expense (in Shares)	4,200
Exercise of stock options and stock appreciation rights - net of	$ 32	(153)		$ 121
Exercise of stock options and stock appreciation rights - net of (in Shares)	31,936			(26,395)		247,500
Other comprehensive income (loss), net of tax					(199)	$ (199)
Net income (loss)			680			680
Balance at Apr. 30, 2021	$ 9,226	$ 57,355	$ (11,457)	$ (6)	$ 291	$ 55,409
Balance (in Shares) at Apr. 30, 2021	9,226,268			1,375		9,225,000