Ever since former interior secretary James G. Watt put a pox on the Beach Boys, rock 'n' roll fans have given low ratings to the Reagan administration's grasp of popular music. Secretary of Education William J. Bennett may have changed all that.

Bennett, who has spent more time in the classroom ministering to the hearts and minds of schoolchildren than any secretary in recent memory, has proclaimed himself "Cabinet expert on rock 'n' roll," and last week took a pop quiz on Pop that bears out his claim.

Two disc jockeys at radio station WCLY offered an on-the-air challenge to Bennett to defend his claim after they saw him quoted in Thursday's editions of USA Today. So Bennett, alerted by a secretary, called them back. "You play it and I name it," he told them.

Bennett didn't attempt to answer the first question -- the names of the five original members of the Rolling Stones -- asking instead for something older. But he scored on who recorded "Locomotion" (Little Eva), on two Pat Boone hits and on who recorded "The Book of Love" (The Monotones). One of the songs he failed to name: "School Is Out."

Turning a Dollar . . . While a recent federal court ruling on the constitutionality of the Gramm-Rudman-Hollings law threatens to take the teeth out of the budget-balancing act, it comes too late to prevent the profitability of the law, which has already spawned an industry. Witness the latest entry in the already crowded field of Washington newsletters: The Gramm-Rudman Report.

The newly minted biweekly is being hawked by Mathis, Belew and Associates at an "introductory price" of $350 a year -- a bit steep unless you consider, as the charter subscription offer suggests, that "no one affected by federal spending or taxes can afford to be ignorant of Gramm-Rudman."

So what gives Mathis etc. the edge on the inside skinny? Why, new partner M. Wendell Belew, former chief counsel to the House Budget Committee, whose "insight on the budget process, politics and Washington institutions is well known on Capitol Hill."

The firm also promises to give quick check-writers dibs on seminars to explain the unfolding drama. And if they don't like the looks of what they read or hear . . . well, Mathis etc. offers the usual range of lobbying services.

Earthquake at Yosemite . . . In the hierarchy of the National Park Service, the job of superintendent of Yosemite National Park is one of the absolute career plums; landing that cherished assignment is like being named ambassador to France or captain of the Navy's biggest carrier.

Thus the Park Service bureaucracy was shaken with earthquake force this month when the superintendent of that scenic California wonder, GS-15 Robert Binnewies, was unceremoniously dumped following revelation of a secret "bugging" episode at Yosemite in 1983.

Park Service Director William Penn Mott booted Binnewies downstairs to a vacant staff slot at the agency's western regional office in response to a report from the Interior Department's inspector general. That report confirmed charges that Binnewies had planted a hidden microphone in his office to make a secret tape of a meeting with members of the National Inholders' Association, a private group often critical of park management. Succeeding Binnewies as the boss at Yosemite will be John M. (Jack) Morehead, currently superintendent at Everglades National Park in Florida.

Changing the Guard . . . In his final week at the helm, Secretary of Agriculture John R. Block, who left office last Friday, exerted the powers of office with some last-minute personnel moves. Raymond D. Lett, who was Block's executive assistant for four years, moves from his current position as assistant secretary for marketing and inspection services to director of intergovernmental affairs. Officials said the move was designed to allow Richard E. Lyng, the secretary-designate, to name his own assistant secretary.

Lett's new job came open when Block moved the incumbent, James B. Boillot, to deputy assistant secretary for governmental and public affairs, a slot left open with the decision of John E. Ford to leave on Feb. 15. Neither Lett nor Boillot will have to undergo Senate confirmation in his new assignment.

Slaughter of the Innocents . . . ? Sources at the Health and Human Services Department say that about 40 Schedule C employes -- political appointees who have no civil service protection -- left over from the regime of former secretary Margaret M. Heckler are being ousted May 1. In some cases, the job slots will simply be eliminated to help the department reach its target reduction of 4,513 jobs under the president's fiscal 1987 budget. In other cases, the slot will be retained but filled with new Schedule C appointees chosen by Secretary Otis R. Bowen and his top aides.

Among the jobs being eliminated altogether are 20 in the 10 regional offices of the department. In the future, none of the offices will have a regional director of intergovernmental affairs or a regional public affairs chief.

Now, the Good News. . . A new General Accounting Office report puts to rest some complaints about mistakes made by the Social Security Administration.

Stories about recipients mysteriously cut off from benefits due to Social Security Administration snafus are almost standard news fare. But the GAO states a different view -- that Social Security offices actually give quite good and courteous service, better than most government agencies.

The GAO surveyed 1,680 Social Security clients, most of whom had recently contacted the agency for one reason or another. It found that 78 percent rated SSA services as good to very good, 15 percent rated services fair and only 7 percent said services were poor or very poor.

The GAO said 50 percent rated SSA services as somewhat better to much better than services from other government agencies; a little over 40 percent said SSA services were about the same as other agencies', and less than 10 percent rated them worse. About 90 percent said that Social Security employes were courteous.

Even among persons who were denied benefits of various types, 50 percent said SSA services were good to very good.