The bill would impose an agreement reached with English Catholic teachers on all remaining teachers and school boards who haven't signed on, as well as ban strikes and lockouts.
But Tory education critic Lisa MacLeod says the agreement weakens the authority of principals and school boards to make calls on hiring and diagnostic tests.
In a letter to Education Minister Laurel Broten, MacLeod says she'll propose the amendments to the legislation if it passes first reading and goes to committee.
The minority Liberals will introduce the bill next week, saying it's necessary to rein in wages and cut benefits to help eliminate a $15-billion deficit.
But they need the help of one of the opposition parties to pass the legislation, which the Tories have signalled that they're willing to do.