The dragon who ate our school

The day the dragon came to call,
she ate the gate, the playground wall
and, slate by slate, the roof and all,
the staff room, gym, and entrance hall,
and every classroom, big or small.

came to call = wie: «kam und besuchte» o.ä.
gate = das (Eingangs-/Ausgangs-) Tor
playground = Pausenhof, Schulhof, Spielplatz
wall = Mauer, Wand
slate = Schiefertafel (hier: Dachziegel)
roof = Dach
staff room = Lehrerzimmer (staff = Personal, Mitarbeiter)
gym = Turnhalle

She's undeniably great.
She's absolutely cool,
the dragon who ate,
the dragon who ate,
the dragon who ate our school.

undeniably = unbestreitbar
great = grossartig
(Der Drache ist hier weiblich.)

Pupils panicked. Teachers ran.
She flew at them with wide wingspan.
She slew a few and then began
to chew through the lollipop man,
two parked cars and a transit van.

flew at them = nachfliegen
wide = breit, weit, ausgedehnt
wingspan = Flügelspannweite
flew = flog (to fly = fliegen)
to slew = herumdrehen, schwenken
few = einige, ein paar
to chew = kauen (chewing gum)
through = hindurch
lollipop man = Schülerlotse. A person who stops traffic by holding up a circular sign on a pole to allow children to cross a road safely
= sich durch den lollipop man kauen, o.ä.

There was some stuff she couldn't eat.
A monster forced to face defeat, 
she spat it out along the street - 
some sandwiches, both veg and meat
and those pink sweets some children eat.

stuff = Krempel, Zeugs, Material
to force = zwingen 
to face = begegnen, konfrontieren
to defeat = besiegen, vernichten
defeat = Niederlage
spat = spuckte aus (to spit = ausspucken)
along the street = der Strasse entlang
both = beide, sowohl als auch