Except as hereinafter provided, for the purpose of receiving state building aid, or other similar aid toward school buildings, which may hereafter be provided, the amount of such aid for cooperative school districts shall apply only to those cooperative or union school districts which were formed from 2 or more districts from 2 or more towns. A cooperative school district formed as a result of a conversion from an authorized regional enrollment area plan shall not be eligible for school building aid for the purchase of property in a pre-existing district which had received building aid for the construction of said building or buildings, provided, however, that any aid for which the pre-existing district is currently eligible shall be continued and shall be paid to the cooperative school district. A cooperative school district formed from 2 or more school districts within one town shall be deemed to be a school district and not a cooperative school district insofar as receipt of state building or other similar aid toward school buildings is concerned. The limitations of this section relative to cooperative school districts formed from districts within one town shall apply only to those which are so organized after July 1, 1955. Such cooperative school district organized prior to July 1, 1955, shall be deemed a cooperative school district for the purpose of receiving such building aid.