Section 305. Assessment methods and standard

1. The existing assessing
  methods in effect in each assessing unit on the effective date  of  this
  section may continue.
    2.  All  real  property  in each assessing unit shall be assessed at a
  uniform percentage of value (fractional assessment) except that, if  the
  administrative  code  of a city with a population of one million or more
  permitted, prior  to  January  first,  nineteen  hundred  eighty-one,  a
  classified  assessment  standard, such standard shall govern unless such
  city by local law shall elect to be governed by the provisions  of  this
  section.
    3. Any assessing unit in which assessments are at full value by reason
  of a revaluation may adopt a level of assessment in accordance with this
  section.