For the Spartan 2's there were 75 of them trained, but 30 died and 12 were crippled in the augmentation, leaving only 33 active. Most of them probably died at Reach.
930 Spartan 3's were trained. the current # of survivors is unknown.
actually for spartan II's, 600 children were trained but this was irrelevent for more than half of these died within the first month