Just to let those who don't know, the PIAA has age requirements and you cannot turn 19 your senior year in high school and still compete in any sport. In fact, you cannot turn 19 by June 30 at the end of the school year so if guys were held back or not, they did not compete their senior years if they turned 19 before June 30 at the end of the year.
Age
To be eligible to participate in grades 10 through 12, you must not have reached your 19th birthday by June 30 immediately preceding the school year. Where you will participate only in grades 7 and 8, you may not have reached your 15th birthday by June 30 immediately preceding the school year; where you will participate only in grades 7 through 9, you may not have reached your 16th birthday by June 30 immediately preceding the school year.
http://www.piaa.org/schools/eligibility/
I will add that you cannot turn 16 by June 30 to compete in grades 7-9
Age
To be eligible to participate in grades 10 through 12, you must not have reached your 19th birthday by June 30 immediately preceding the school year. Where you will participate only in grades 7 and 8, you may not have reached your 15th birthday by June 30 immediately preceding the school year; where you will participate only in grades 7 through 9, you may not have reached your 16th birthday by June 30 immediately preceding the school year.
http://www.piaa.org/schools/eligibility/
I will add that you cannot turn 16 by June 30 to compete in grades 7-9