School Lake
School Lake in Chisago County, Minnesota has a water quality grade of A (Excellent). Water clarity: 7.9 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 1.8 µg/L.
- Clarity
- 7.9 ft
- Mean depth
- ~20 ft est.
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Chisago County
School Lake is a mesotrophic lake in Chisago County, Minnesota with an estimated average depth of about 20 feet. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 29 other monitored lakes in Chisago County, School Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-19. Grade methodology: LakeGrade methodology.
Watch School Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Moderate clarity, visible to about 7.9 ft. Phosphorus level: 20 µg/L. Chlorophyll-a: 1.8 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.9 ft | Not graded |
| Phosphorus | 20 µg/L | Good |
| Chlorophyll-a (Algae) | 1.8 µg/L | Good |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near School Lake
Compare lakeside cabins, hotels, and vacation rentals near School Lake in Chisago County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near School Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~20 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for School Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Green LakePublic
Fishing School Lake
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.069 m/yr | 6 |
| Phosphorus | ↑ Improving | -11.17 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -11.14 µg/L/yr | 6 |
EPA Impairment Status
School Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN13-0057-00 · Official waterbody report
County Ranking
Ranked #4 of 30 lakes in Chisago County
Nearby Lakes in Chisago County
Frequently asked questions about School Lake
What is the water quality grade for School Lake?
- School Lake in Chisago County, Minnesota has a water quality grade of A (Excellent). Water clarity: 7.9 ft visibility. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 1.8 µg/L.
Is School Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. School Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 1.8 µg/L. Always check local health department advisories before swimming.
How deep is School Lake?
- No published bathymetric survey covers School Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 20 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on School Lake?
- School Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Green Lake. Public access is listed as yes.
Explore School Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Chisago County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the St. Croix Watershed, ranked by water quality
Moderate nutrients, good water quality
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near School Lake
Other Grade A Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
105 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA105 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Secchi Transparency Tube, 100 cm
- Phosphorus by Two Reagent Colorimetry
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
- 10200 H ~ Chlorophyll a-b-c Determination
- Analysis of Chlorophyll in Periphyton and Plankton
Monitoring station identifiers (2)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory