IN PRINCE GEORGE'S County -- there a diverse and proud constituency looks constantly to its local government -- Tuesday's elections could have a major impact. The contests for county executive, county council and school board are related and pose critical choices bearing on the quality of public education and on financial stability.

For county executive, Prince George's should welcome Democrat Parris Glendening's forward-looking approach, and his council experience offers an attractive contrast to the small-bore skirmishing of the last four years. He has been forthright in his support of the modest change in the TRIM formula that is essential to improving the schools, fighting crime and taking other necessary measures.

Thoughtful residents who can see beond the day after tomorrow surely recognize that even a well- meaning attempt to set a flat-dollar ceiling on county revenues cannot work forever. The candidates who sense this danger, and are politically courageous enough to say so, deserve support.

For the county council, there are incumbents and challengers alike who deserve attention.

In the 1st District, incumbent Democrat Frank P. Casula has concentrated on constituent services and, unlike his challenger, recognizes the necessity of modifying TRIM. In the 2d District, Democrat Anthony Cicoria understands the impact of teacher shortages and seems willing to examine difficult financial questions. James M. Herl, a Democrat running in the 3d District, shares this understanding, as do Democrats Richard J. Castaldi in the 4th District and incumbent Floyd E. Wilson Jr., who is unopposed in the 5th District.

The 6th District's stronger candidate is JoAnn T. Bell, a Democrat who served effectively on the school board. In the 7th District, Democrat Hilda R. Pemberton offers promise. In the 8th District, incumbent Democrat Sue V. Mills is less impressed with the severity of cuts in school budgets and is content with TRIM, but her opponents have even narrower views. In the 9th District, incumbent Democrat William B. Amonett has had a lively challenge from Republican Ella E. Ennis, although neither takes a clear enough position on financial issues.

For the school board, the knowledge and good sense of member Lesley Kreimer will continue to be an asset; she is unopposed in the 2d District. In the 5th District, voters may be well served by either Nancy C. Cummings or Paul R. Shelby, who both offer solid records. In the only other contest, in the 8th District, challenger Otis Ducker could prove a refreshing change from the narrow representation that incumbent Angelo I. Castelli has provided for the last four years. Mr. Ducker has shown a keen interest in the complexities of a county system that must respond to diverse educational demands.