While a redevelopment plan for downtown Columbia lurches closer to reality, fresh questions are surfacing about whether neighborhood schools will be able to handle more students who will be living in the new housing.County and school system planners have expressed qualified confidence that existing planning reviews and approval processes are giving them a good picture of the school needs ahead.They know, for instance, a new middle school will be required and that Running Brook Elementary School in west Columbia, near downtown, will be well over capacity by 2019.Projecting school enrollment is a bit art and a bit science that's done on local and state levels. Over many years, most projections have been solid and Howard, unlike some of its neighbors, hasn't had to rush portable classrooms into place.The state estimates that Howard's schools will have the largest percentage increase of students in the state between now and 2024 and that statewide, the number of middle school students will rise "substantially" in the next eight years.Enrollment changes for a number of reasons, including the economy and construction of new housing, birth rates, private school students moving into the public system and immigration. Howard's schools are projected to have about 62,000 students by 2024, up from the 54,000 entering classes last week. (This school year's enrollment is up by about 1,000 students over last year.)Whether the largest pockets of enrollment growth will come in Columbia remains to be seen, as debate continues over how much affordable housing should be built and whether new units in downtown Columbia will cater more to empty-nesters or young families. So far, the newer housing has fewer school-age residents than traditional planning models suggest.The school system has time to get things right and planners realize that flexibility in planning is critical. Their goals need to include keeping any boundary changes to a minimum, maintaining reasonable class sizes and having a communications plan about their growth strategy that keeps parents, taxpayers and elected leaders in the loop.