The Senate passed Amendment 196 on District Determined Measures

...what does that mean?
The first thing is that this, along with anything else passed by only one of the two bodies, goes to conference committee. Assuming it comes out of conference committee and survives Governor Baker's veto (either by not being vetoed or by the Legislature overriding his veto), it would then become part of the law.

The meat of what the Senate passed is as follows:

‘Notwithstanding any other provision of the general or special laws, the board shall not mandate any school district to include as part of an educator evaluation system or as a teacher performance standard the use of student performance data that is intended to measure an individual educator’s impact on student learning, growth, or achievement'

...which would forbid the state to require districts to use student performance as part of teacher evaluation. Districts could still do so (subject to collective bargaining), but the state could not require it.