ATC GROUP SERVICES INC. AND SUBSIDIARIES EXHIBIT 11 COMPUTATION OF EARNINGS PER SHARE THREE MONTHS AND NINE MONTHS ENDED NOVEMBER 30, 1996 and 1997 (Unaudited) - -------------------------------------------------------------------------------- Three Months Ended Nine Months Ended November 30, November 30, -------------------------------- -------------------------------- 1996 1997 1996 1997 --------------- --------------- --------------- --------------- Primary Earnings Per Share: - --------------------------------------------- Weighted average number of shares of common stock outstanding................... $ 7,792,964 $ 7,886,057 $ 7,789,104 $ 7,830,784 Additional shares assuming exercise of dilutive stock options and stock warrants.. 661,187 724,596 748,167 684,431 --------------- --------------- --------------- --------------- Total average common and common equivalent shares outstanding........... 8,454,151 8,574,553 8,537,271 8,503,018 =============== =============== =============== =============== Net income.................................. $ 1,506,278 $ 1,179,710 $ 5,326,074 $ 3,604,065 =============== =============== =============== =============== Earnings per common and dilutive common equivalent share.................... $ .18 $ .14 $ .62 $ .42 =============== =============== =============== =============== Fully Diluted Earnings Per Share: - --------------------------------------------- Weighted average number of shares of common stock outstanding................... $ 7,792,964 $ 7,882,057 $ 7,789,104 $ 7,830,784 Additional shares assuming exercise of dilutive stock options and stock warrants.. 661,187 743,024 781,066 729,664 --------------- --------------- --------------- --------------- Total average common and common equivalent shares outstanding........... 8,454,151 8,592,981 8,570,170 8,548,252 =============== =============== =============== =============== Net income.................................. $ 1,506,278 $ 1,179,710 $ 5,326,074 $ 3,604,065 =============== =============== =============== =============== Earnings per common and dilutive common equivalent share.................... $ .18 $ .14 $ .62 $ .42 =============== =============== =============== =============== F-25