IMHO, do not take this generic advice.........Bat length and its subsequent weight are not something you should just guess at. A 33/30 is well used in HS, but I do not think it's worth wasting your money just because someone thinks its perfect for a average HS player.
You know your son. The right fit depends on his height, weight, strength and swing type. There is a good test to determine proper length and weight for his body strength. Have him grip the bat in his strong hand. One hand at the bottom of the grip. Have him hold it out straight from his body. Kind of like Thome does. Have him hold it for 30 seconds.... If its too heavy or long, he will not be able to hold it still or level. Repeat at a lower weight or length until he can hold it still. You will find it is pretty easy to tell if he can handle it.
I cant tell you how many young HS players come to the plate using too big a bat. It may only seem like an inch or an ounce, but if its too big it effects the swing enormously. Plus strictly from a financial aspect, you cant afford to waste $199-$299 on what an average HS baseball player uses.