ONCE AGAIN that old political clock on the prison wall in Maryland shows it's time to bid farewell to the state's current school of thoughts on corrections policies and to make way for the opposite extreme--to shift from let-'em-all-out to lock-'em-all- up. Gov. Harry Hughes, whose early attempts at enlightened corrections policies fell apart after an overdose of loose supervision that led to a string of escapes and crimes by inmates, is now focusing on tighter incarceration programs. But just as the first approach failed, so may this latest overemphasis on bigger prisons with populations to match.

Right after inauguration, Mr. Hughes was reluctant to support construction of any large prison facilities. But now he's ready to urge the building of a new medium-security state prison with at least 500 beds, probably in Hagerstown. This project won't sit well with the students of the free-everybody school, even if there is evidence that more space is needed. But continued double-celling of inmates in cramped quarters is no substitute for additional facilities.

The rationale being given for the move is that it is part of the governor's effort to compromise with those legislators who bitterly opposed his earlier emphasis on larger release programs instead of larger prisons. If this proves to be the case, fine; but other policies and guidelines for release of inmates appear to disqualify all but a small pool of inmates for pre-release, and other in-community programs are being assigned to the state's already jammed prisons. From there the story gets all too familiar: more cells, more people imprisoned, more calls for still more facilities.

But why throw out either policy entirely? Along with more cells to relieve crowding, there can--and should--be more supervision and better administration of work-release, parole and other rehabilitation efforts. The point isn't to conduct state-sanctioned, law-breaking sprees for violent criminals out on the town--but neither is it to fill up huge prison complexes with everybody from double-parkers to rapists. Instead of shifting from one extreme to the other, Gov. Hughes and responsible policy-makers in the legislature should settle on an approach that combines tight administrative controls with flexible, monitored policies of incarceration and release