The Harvard Summer School, bigger and cooler than ever, begins its 91st session today.

It is bigger than last year by about 200 people--some 5000 students are expected to attend classes. Two dozen courses are over-enrolled.

It is cooler because two more buildings now have air-conditioned classes--Larsen Hall and Emerson. There are only a few classes left that are not air-conditioned, according to Thomas E. Crooks, director of the Summer School.

Crooks is not worried about the increased numbers. The biggest problem was to find living quarters for female students, and that has been solved. Girls will occupy Quincy House and every dormitory in the Yard except Holworthy, which will house the International Seminar.

More people means longer queues at meal time, so this summer Quincy House will be open Monday through Friday to relieve the crowding in the Union. On weekends, however, everyone will have to brave the Union lines.

Crooks admits that it may not be so easy in future years to solve the space problem. That means a more selective admissions policy may be necessary.

More students were rejected this year for academic deficiency than ever before, but the number is still very small--about 50. Next year, according to Crooks, the application form may be lengthened to provide more information about prospective students.

Only five years ago, in 1961, no application at all was necessary. If you wanted to attend the Summer School, you simply came to Cambridge and registered.

Most of the School's vital statistics have not changed drastically from last summer. The breakdown will be 52 per cent men and 48 per cent women -- a little less than a woman for every man. About one out of four will be a Harvard or Radcliffe student, who will be glad to show you the sights.

Summer Grades

Providing past percentages prevail, one out of eight students figures to squeeze out at least one grade below C-. But almost two out of three will get nothing but A's and B's -- a much higher percentage than Harvard-Radcliffe students manage during the academic year.

Expenses, of course, have gone up. Tuition has increased $10 per half course, but room rent and price per meal remain constant -- except that board is now 21 meals a week instead of 15. The entire operation costs some $1.1 million, about ten per cent above last year. But the Yard Punch, every Wednesday, is still free.