Arashi Waku Waku Gakkou @ Tokyo Dome tickets will be available to the public. ^^
Participating ticket agencies listed on JNet will start selling the tickets on Saturday, 18 June 2011 from 10:00 a.m.
Price: 4 000 Yen (~US$50)
I added the websites for reference.
CNプレイガイド :(初日特電)0570-00-0056
CN Play Guide: cnplayguide.com
ローソンチケット :(初日特電)0570-00-0013
Lawson Ticket: l-tike.com
イープラス :(初日特電)0570-06-9930
E Plus: eplus.jp
チケットぴあ :(初日特電)0570-02-8813
Ticket Pia: t.pia.jp
キョードー東京 :(初日特電)0570-08-9988
Kyodo Tokyo: kyodotokyo.com
If you're in Japan, it's worth a shot to go to Arashi Waku Waku School. ^^
Good luck!