NBC sets up another household of charming children. `Day by Day' brushes by some doubtful premises

Day by Day NBC, previews Monday, 8:30-9 p.m. and Thursday, 8:30-9 p.m.; premi`eres Sunday, March 6, 8:30-9 p.m. Executive producers: Gary David Goldberg and Andy Borowitz. Stars: Doug Sheehan, Linda Kelsey, and Julia Louis-Dreyfus. In an attempt to garner the largest possible audience for a new series before it settles into a regular run, NBC is scheduling two previews of ``Day by Day'' before the show premi`eres in its regular Sunday time period March 6.

To judge from the initial preview (the only one available for screening at press time), ``Day by Day'' has all the earmarks of a potental winner: an amusing premise, skillfully written dialogue, expert acting by its stars, and one factor that's simply unbeatable - a houseful of charming and amusing children.

The premise? Kate and Brian Harper, married lawyer and stockbroker, give up their yuppie careers to run a day-care center in their home in order to spend more time with their infant daughter and teen-age son. If there is a major fallacy in the premise, it is the assumption that running a day-care center doesn't require skilled training; that parents are not taking a great risk by placing their children in the care of inexperienced managers, who hire teen-agers with no more credentials than one year of child psychology courses.

But, that reservation aside, ``Day by Day'' gets lots of laughs with its portrayal of adult attitudes toward children, as well as children's attitudes towards adults. Some typical samples of its humor:

Kate Harper is planning to take the kids on a field trip to the stock market. ``There's only one condition,'' she explains. ``They want the kids all to be shackled together.''

When the children sing ``Old MacDonald Had A Farm,'' one child insists that farm is spelled F-A-R-M, rather than E-I-E-I-O.

A lesson in sleeping over at a friend's house elicits the unsolicited comment that one child has an Uncle Steve who sleeps in the same room as her mother. ``It's time for some outside exercise,'' Kate quickly orders, ending the lesson.

Executive producer Gary David Goldberg is also the creator of ``Family Ties.'' He has given the initial episode of ``Day by Day'' some of the unexpected role-reversals found in ``Family Ties.'' What results is funny, sassy, poignant, and totally contemporary. Based on the track record of Goldberg, ``Day by Day'' could turn out to be the 1988 season's most relevant new hit.