For seven years, teacher Chan See Yeu crafted her lessons around physics concepts like electromagnetism, the laws of motion and the transfer of heat.
These days, however, her learners are a few years younger and she tells them about basic facts like why living things need water, food and air to survive.
The 36-year-old made the switch to teach at a primary school two years ago. She had begun her career at North View Secondary in 2008 as a physics teacher and now teaches science at Northland Primary School.
Ms Chan is among a growing group of teachers being redeployed from higher to lower levels - from junior colleges (JCs) or secondary schools to primary schools, and from JCs to secondary schools.
It is a trend fuelled by a shrinking student population that has led to more schools merging in recent years. This year, MOE announced 14 schools, including JCs, would be folded into others by 2019.
Some 340 teachers have made the transition to primary schools this year, the Ministry of Education (MOE) told The Straits Times. This is up from just 90 teachers last year. In 2015, only 18 higher-level teachers moved to primary schools.
These cross-deployed teachers can help to bridge the gap between one education level and the next, and thus help its teaching force to "deliver better teaching and learning outcomes", said MOE.
JUST LIKE STARTING OVER
When I was given a choice to make the switch, I thought I should give it a try and step out of my comfort zone... Frankly, I felt insecure as I had not taught primary school kids before.
TEACHER CHAN SEE YEU, on teaching science at Northland Primary School.
"For example, secondary school or JC teachers who are posted to primary schools can help to deepen subject specialisation among teachers at the primary level too," said a ministry spokesman.
"This will, in turn, help primary students to build strong foundations in core subject areas before they move on to secondary school."
There are currently more than 33,000 teachers in Singapore.
Many teachers make the switch to expand their repertoire of teaching skills. But for Ms Chan, a mother of two boys aged four and seven, the switch was akin to starting her teaching career all over again. "Frankly, I felt insecure as I had not taught primary school kids before."
She had to undergo a bridging course, held weekly for about five months by the Academy of Singapore Teachers, which allowed her to go for classroom observations at various primary schools, among other things.
Now, such teachers will go through a more structured bridging course held daily for about five weeks. It equips them with necessary pedagogical skills and knowledge to teach at the lower levels.
One change that Ms Chan made was to include hands-on activities for her younger learners. For instance, she takes them to the garden to observe various flower parts and dissect the blooms to learn about the functions of their anatomy.
"We cannot expect them to be able to understand by just reading texts in books or notes," she said.
Many redeployed teachers, having taught subjects at an advanced level, are able to explain concepts at a deeper level whenever their students are curious to know more.
Mr Brandon Lim, 33, who taught at St Andrew's JC and joined Gan Eng Seng School this year as a history teacher, would share with his graduating students about the JC curriculum. "I am able to advise them on whether a JC education is really suited for them," he added.
Observers believe that getting familiar with a different syllabus and fine-tuning teaching styles to suit younger students takes time, from a few months to a few years.
However, National University of Singapore lecturer Kelvin Seah said that cross-deployed teachers can offer students some continuity.
"They are in a position to let students see how the things studied at the lower level will be useful in comprehending what is to come next at the higher levels," he added.