Theodore R. Sizer, Dean of the Graduate School of Education urged the parents and teachers of the Shady Hill School to cooperate more fully with the public and parochial schools of Cambridge, last night.

More than 700 people were gathered at Shady Hill, a private elementary school in Cambridge, to celebrate the school's 30th aniversary. The school's enrollment of 425 includes a large number of Harvard faculty children.

Sizer aserted that Shady Hill should accept "as an article of faith, that there is much fine teaching going on in Cambridge public and parochial schools. I get mad when private school parents tell me they won't send their children to public schools," he said.

Citing Shady Hill's history of cooperation with other private schiols, he said the school had failed to take advantage of "a great dversity of schools within walking distance." He said there are 17 public and 18 parochial schools in Cambridge.

Sizer urged the school to carry on new experiments in progressive education. Noting that children grow at different rates, he asked if grouping students by age was realistic. He said that present day systems of marking pupils should be reevaluated.

Sizer was interrupted for applause when he noted that the Cambridge School Committee had voted Tuesday night to join the Ed School's new center for educational research and development. The center, which has received a $2.4 million grant, will conduct a five year program of cooperative development with Cambridge and four other greater Boston school systems.

Also speaking at the banquet were Katherine Taylor and Edward Yeomans former directors of Shady Hill.