A new study of the Rev. Jesse Jackson's PUSH-EXCEL educational experiment says that, despite some improvement in the program, Jackson has not translated his inspirational message into a workable system to help disadvantaged children do better in school.

The study, conducted by the American Institutes for Research under a contract from the Department of Education's National Institute of Education, is the third unfavorable evaluation in the past year of the federally funded demonstration project, and comes as Jackson's federal grant is up for renewal.

The project, involving more than three dozen schools in a number of cities, is being funded by $3 million voted by Congress. The evaluation covered schools in Chicago, Los Angeles, Denver, Buffalo, Kansas City, Mo., and Chattanooga, Tenn.

The report says activities are sporadic and often one-shot, with little follow-up, and there is no systematic plan for taking the program beyond its first step -- an inspirational address by Jackson or some other leading figure.

In that address, Jackson tries to instill in the students a determination to learn, better themselves, achieve, exercise self-discipline and succeed.

The next step is to take advantage of the initial burst of enthusiasm by getting the student to pledge a variety of activities, such as regular school attendance and two hours a day of study without television.

Also part of the program are academic games, participating in after-school PUSH-EXCEL clubs, and systematic contacts with parents, teachers and community leaders to surround the children with an atmosphere of concern for and approval of their efforts.

Since 1975, a number of school systems have been trying to install the PUSH-EXCEL concept, in part with local and private funding and more recently with federal money -- $2 million so far with $1 million pending.

The latest evaluation says that the program has made some progress. PUSH-EXCEL has developed its first primer to describe the program to teachers and communities, and a guide on activities to nurture the student's desire to learn. The study also says an internal monitoring system is being developed, and training of personnel is being upgraded.

But it says that overall, the experiment has not resulted in a solid, ongoing program or follow-up methodology that can be applied on a wider basis.

Statistics in the report do not indicate any measurable educational improvement nor pattern of improvement in absenteeism or dropout rates.

President Reagan has proposed that the $1 million a year Congress has voted as a separate line item in the U.S. budget to fund Jackson's program be included in a broad educational "block grant." That would wipeout the designated funding, but the experimental program could be continued by the Department of Education from its own general research funds.