Brookline school officials have approved drastic changes to a controversial proposal that would have excluded a number of homes straddling the town line from the public school district. The Brookline School Committee approved a new policy in late January requiring that at least 25 percent of a dwelling be in Brookline to qualify as part of the town’s school district. But the new policy will grandfather all single-family dwelling units on the town line that have been considered part of the school district and were purchased on or before the new policy was approved, said School Committee member Rebecca Stone. Brookline had been considering a new policy that would exclude dwelling units at more than 30 different addresses from remaining in the school district if the homes were sold and the town didn’t assess property taxes on at least 50 percent of the property. The proposal drew a backlash from a number of homeowners who said it would decrease the values of their homes. Stone said under the revised policy that has been approved, homes purchased before the policy change will still be considered part of the school district when they are sold unless they are developed in a way that more than a single family will live in the dwelling.