I love Project BudBurst and had my own elementary education students observe seasonal events in dogwood trees for several semesters, but never got around to submitting their data on the BudBurst website. So I think I can suggest several ways for BudBurst to encourage more "follow through".
(The drawing shown is copyright-free and comes from USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 2: 664.)
One reason a teacher may not "follow through" by uploading their data is lack of confidence in identifying plants and phenophases (seasonal events). One idea to address this would be for BudBurst to emulate Project Noah (http://www.projectnoah.org/), which encourages the uploading of photos recording participants' observations and the giving of feedback on their identifications.